Post by Bill Von Sennet on Aug 22, 2008 22:07:58 GMT -5
Tom Goodrick
FLYING PISTON TWINS
« on: Oct 7th, 2007, 3:43pm »
PART 1 INTRODUCTION
We'll start the section on flying twins with the Beech Baron 58. Everybody has this and has probably tried flying it. It is fairly easy to fly if you have worked on the faster singles like the Mooney. Next we'll get into high altitude work with the Cessna 340, a pressurized and turbocharged twin you can get from my web site. But before getting to the specifics of flying each aircraft, there are several basic differences we should discuss between flying twins compared with singles - some obvious and some not.
The only reason most people buy a twin is to have the extra engine when one engine stops running. Many people today fly the large and fast singles over water, at night and in IMC conditions without qualms about engine failures. They can do this because the statistics support the safety of the single engine aircraft of today. At least that has been true many years ago. Today it might not be so great an idea because many of the fast singles are getting old enough to lose some reliability. As a pilot in training with a single-engine airplane, we are taught to be ready to land a single in any reasonable space when the engine quits. On takeoff after the runway disappears behind you and before you reach 1,000 ft, you have no choice but to land dead ahead, trying to miss the hard things. Odds of survival doing this are about 50% at best. Once you are above 1,000 ft you have more choices and can even land on a runway. Your odds of survival increase dramatically to at least 80% although the odds of ending up with an unbent airplane may be 10%. I did it once in a loaded Cessna 150 on a snowy field. We were even able to take off after clearing the carburator ice from the engine. (I was with my instructor but I did all the flying.) Of course, today you can buy an airplane with a parachute. But my experience with parachutes and with parachute landing of heavy items like airplanes makes me doubt the wisdom of it. I'll take an airplane gliding landing any time over a chute. People unlucky enough to land on hard surfaces will probably break their backs with a parachute - if the chute does not oscillate. If it does oscillate and hit on a road or parking lot, they'll break more than their backs. When you fly singles at night or over water, which I have done with plenty of time to consider the possibilities, you realize you will have few choices when the noise stops. IMC (Instrument Meteorological Conditions) is another roll of the dice. As you come out of the overcast, you have a slim chance of being able to glide to a safe landing site. That's why people like to buy twins. They even have a new option to shut down an engine before it is ruined if a temp guage starts looking bad.
In training for flying twins, you learn not to lift off just because the plane is going fast enough so you won't stall. You takeoff when you have enough speed to continue the flight if an engine quits. You practice that condition, first at altitude and later closer to the ground. You must first identify the engine that has quit and then push on the rudder pedal on the opposite side. this is actually an extremely unusual event and very difficult to handle. You are too low and slow to be wallowing around trying to handle the unbalanced thrust. Having an engine shut down at altitude is fairly easy to work with safely. Still, however, it is significant to note that any loss of an engine must be treated as an emergency situation and the pilot must land at the first airport reasonably accessible. Some leeway is granted in this regulation if the pilot feels he has good control of the situation and wants to land at an airport with a long runway. Such airports generally have better repair facilities as well. I demonstrate such a situation where I pass up a few airports to land on a long runway with an ILS because it happens in IMC over mountains.
Twins are more than twice as expensive to operate. Many will carry no more payload than many singles. They all carry a lot more fuel that has to be managed properly during the flight. Keep the fuel balanced or you will have lots of fun when you have to shut down an engine. All twins will have plenty of climb rate when both engines are operating. They have to be designed to get to a flying condition after losing an engine a little after takeoff. This is when the good engine is operating at full power and producing a lot of yaw that must be countered with rudder. Some people say your odds of having an engine quit on takeoff are doubled in a twin. It is still pretty slim. The training program for transition to a twin involved many parctice climbs and other maneuvers on one engine - either engine. According to most statistics, your odds of dying when an engine quits are significantly worse in a twin than in a single. That is because the single pilot is trained to find a good landing site as soon as the engine quits. The twin pilot tries to mess around and get to an airport. He often ends up stalling out as he gets too slow turning final and spins in.
When you fly twins in FS, spend some time flying them with one engine out. In the Baron 58 at max gross weight, the climb rate will be 1750 fpm with both fans turning and only 394 fpm with only one fan. Flying twins on one engine requires patience.
In the US, the FAA requires single-engine aircraft have a landing stall speed below 61 KIAS. Twins do not have this limitation. Designers have given twins higher speed with smaller wings for the weight (ie- higher wing loadings). This is an easy, low-tech approach. But it means you'll have a tough time if both engines quit as when you run out of fuel. It also means every landing and takeoff is a little faster than in a single. Thus it requires a little better pilot skill level.
When flying twins, it is usually more important to learn and to watch all the required speeds and procedures. To lift off well, many twins require one notch of flaps. Thus, as soon as you lift off, you are busy raising the gear and the flaps. You must also stay low over the runway until you have VMC which is the minimum control airspeed at which the rudder has enough power to keep you straight if one engine is at full power while the other engine is at zero power. This number is not easily found for many aircraft so I use the rule of thumb that VMC is 10% above clean stall speed.
Be aware that there will generally be more of a trade-off to make between payload and fuel because the fuel is a larger percentage of the max gross weight in many cases. In many twins, all the back seats have to be empty if you fill the tanks. This means you have to figure the fuel burn for a trip and carry only enough for the trip (or for one leg of the trip) plus 45 minutes of extra cruise to get to a new landing site if the first does not work out. Another complicating factor is that many twins have a max landing weight (MLW) that is significantly less than the max takeoff weight (MTOW). Thus for short trips with big loads, you may have to keep the fuel load low to be under MLW when you arrive at the destination.
Twins cruise high and fast. This will require some planning when you get near the destination - or even within 50 nm of it. You will have to know the safe speed for extending gear, and the safe speed for extending flaps. The general power setting that works for getting down from cruise to an altitude for the approach to the area near the airport is 15 inches MP and 2100 RPM. in many cases this will get you down close to gear speed or flaps speed shortly after you level off near the airport. It is customary to put the gear down at that time. Note that in some cases, the flaps can go to the first notch at a higher speed than the gear can be extended. In this case the flaps go out first and help slow the plane for gear extension. In most cases both the first notch of flaps and the gear will be extended as you start down final approach. In unpressurized aircraft like the Baron, you must keep the descent rate no greater than 500 fpm and manage the mixture to keep enough power.
Twin pilots are generally a lot busier than single pilots. They have twice as many engine gauges to look at, twice as many levers to push or pull and twice as many switches plus a few more like synchrophasers. Fuel management becomes an issue even in FS. I use the Baron power quadrant with the fuel switches on all piston twins. With many aircraft as you fly, one engine takes more of the fuel than the other. You have to watch this and switch the fuel to cross-feed off the low tank to keep the tanks balanced. I have flown on many twins where the pilots had trouble synchonizing the engines. This can drive you nuts, hearing and feeling the out of synch vibrations. In FS we don't have much of a problem. If you get one engine slow, just shove both throttles forward and draw them back as one.
The fact that you must fly final about 20 knots faster than in singles is another issue. Indeed 20 knots is about the difference in final approach speed for each level of sophistication: 70 KIAS for singles, 90 KIAS for twins, 110 KIAS for turboprops and 130 KIAS for bizjets. You have to handle the power changes, trim changes, gear and flaps as the runway rushes at you faster and faster. That is why I strongly urge people to work their way up through the different levels of difficulty, getting very profficient at one before moving up to the next. Unfortunately, I keep getting rusty at the more challenging aircraft and have to re-learn the procedures all the time when I go back to them. i may have to adopt a rule such as:
Fly jets every Monday and Tuesday, turboprops every Wednesday, piston twins on Thursday, singles on Friday and anything, including helicopters on weekends!
That would help maintain proficiency!
« Last Edit: Oct 8th, 2007, 12:03am by Tom Goodrick »
Tom Goodrick
Re: FLYING PISTON TWINS
« Reply #1 on: Oct 7th, 2007, 6:09pm »
FLYING TWINS PART 2
BARON 58 FROM KCHA TO KAVL AND BACK
We'll give the Baron a typical job. We'll fly empty (one pilot) from Chattanooga TN to Ashville NC and then pick up 4 passengers with luggage for the return flight. We check the amount of fuel that can be carried with the four pax figuring 4(180+20)+220 for the pilot (me). Then we add less than an hours' fuel for the trip out (20 gal) and start with that fuel but with an empty cabin. This will give us max fuel coming back.
At the start we load 59 gallons per side. Now we have 118 gal, 4838 lb gross weight. We enter a GPS direct flight to KAVL. We check cowl flaps - open. Check fuel switches - both up. Fuel Pumps - High. We set the autopilot - HDG 020, ALT 7500 ft. There is no wind so takeoff will be made on runway 2, which takes us away from the city. We switch on the beacon and the strobes. We verify that the flight plan is in the nav computer. We set the trim at 7 degrees for takeoff. Flaps are up. We taxi to runway 2. We stop at 2 and note it is 13:03. Time to go.
We swing into place on runway 2 and are cleared for takeoff. The throttles go full forward. 90 KIAS comes quickly and we rotate and fly away. Gear comes up. At 1000 ft above ground we set the autopilot ON and set the climb rate for 1200 fpm. Soon after that we turn to 090 to intercept our course. We reduce the RPM to 2500 and climb at about 72%. At 5,000 ft we lean for max fuel flow. We see 75% power briefly climbing through 6300 ft for our cruise altitude of 7500. All the engine numbers are in the green - literally - meaning all is okay. At 7500 ft the autopilot levels us and we lean once again for best power (max fuel flow). The power turns out to be 70%. That's the best we can do at this altitude. We continue on a heading of 090 even though that shows convergence with our flight plan path about 20 miles ahead. This is a VFR flight. If it were an IFR flight, we could converge earlier. It is time to enjoy the great scenery. The nav computer says we have about 30 minutes.
I switched the fuel pumps to low during cruise. The ground speed (same as true airspeed with no wind) was steady at 202 knots. Airspeed was 182 KIAS. The scenery now includes mountains and rivers - very picturesque. We adjust the ILS arrow to point to 340, the runway heading for our landing. We will soon deviate from the straight course to the airport to get in position for a descent along the direction of 340 which will keep us in the middle of a valley leading to the airport. Some of the mountain peaks are over 5500 ft in the area. The airport is at about 2200 ft msl. There are no weather problems on this trip because we have turned the weather OFF. We'll get hit with some storms on the way back.
Okay, we are 34 nm out. I am going to turn 20 degrees right of our course to get a good offset for the descent. This worked fine. At 10 nm on a diagonal from the airport, I was ready to start the descent. The high rocks had cleared from the circular path I wanted to take getting lined up with the runway for a straight-in final from 5 nm out. This is a case where you must use the GPS map in relief mode to see where the high rocks are. The radar altimeter is very useful too and helps you interpret the elevations shown on the relief map. I pulled the throttle back to 18 inches and then the RPM back to 2100. I shut off the autopilot and begane the circular descent. Soon it was evident i need to slow more and descend a bit steeper so I pulled the throttles back to 15 inches. I ended up too high and too fast even after slipping a bit so I turned left from the runway direction and did a gentle 360. There was no traffic. (I never turned that on for this flight.) During the turn, which was well inside the valley, I slowed enough to get a green light for the gear and i knew that when the gear can go down, the first notch of flaps can go out. When the runway came around again I was about 2 nm out and just under the visual glideslope at 111 KIAS as I let down full flaps. Over the fence I cut the power to idle. The landing was nice at 77.22 KIAS and -150 FPM. At 14:53 we were parked. (We had crossed a time line just after leaving Chattanooga. I parked and headed for the Berry Patch Cafe for pie and coffee and to meet the passengers. I didn't notice the rain clouds forming just west of the peaks to the west and moving our way.
I had time to eat my pie, sip my coffee, meet the passengers and get them into the plane before the deluge hit. The right seat got pretty wet as I climbed in. I started the engines and let them idle while I filed the flight plan back to Chattanooga. The fuel was down to 45.7 gallons per side - just right for the increased load. The gross weight was now 5479 lbs and the CG was not at 29.05% MAC. This would be quite a different aircraft than the one I flew over. As the rain hit the wind was gusting quite a bit. The heavier weight would make for a steadier ride in the gusty wind. The wind was from the north so we would use runway 34. I set the autopilot for 340 and 8000 ft cruise altitude.
Fuel selectors up, mixture and prop forward, autopilot set but not ON, fuel pumps on High, strobes and beacon on for taxi, fuel good, weight and CG good. We were ready to taxi. Trim went to 7 degrees as we taxied out at 16:00. Visibility was good for takeoff. We could see most of the runway! At 400 feet we turned on the autopilot. The mountains on either side were in the haze, rain and clouds so we stayed on runway heading until reaching cruise altitude of 8,000 ft. We had been climbing at 1200 fpm but that was too much in the rain. We reduced that to 800 fpm and adjusted the mixture at 6,000 ft.as the airspeed continued to drop we reduced the climb rate to 200 fpm at 7500 ft. Then we started to get more airspeed. At 8,000 ft we had 105 KIAS and we turned to 220 degrees to get back on our course. With the wind at 19 knots from 90 degrees we had a nice groundspeed of 207 knots. But we could only gte 61 % power so our indicated airspeed was only 168 KIAS. We were still in the rain and the clouds (using "Stormy Weather"). At 8,000 ft our radar altimeter read 2,000 ft as a nasty-looking peak passed nearby on our left. As we turned onto course for Chattanooga, the groundspeed increased to 215 knots with the wind more directly on our tail (wind 90 dgrees and course now 265 degrees). There was probably some pretty scenery underneath us but we couldn't see it in the clouds and rain. Leaning produced only 14.40 gph per side for 61.25% power.
About halfway there the rain stopped but we were still in clouds so we set the radio for the ILS to runway 2 at KCHA (108.3 and 019 degrees). 40 miles out we made a jog to the south of course to get the offset for the turn onto the approach. We turned to 232 degrees. It started to get lighter out and we could see the ground far below (5,000 ft below) for a brief moment and then the rain started up again and it got dark. At 33 nm out we were past the tall mountains so we could descend to 6,000 ft. We reduced power to 15 inches and 2300 rpms (30.9%). At 25 nm out we could turn to 260 degrees. This put us on a tangent to the 10 mile circle around KCHA. At 6000 ft we leveled and brought the power up to 60% with an increase in the manifold pressure to 22 inches. With the wind drift we were closing fast on the circle so we continued down to 4,000 ft. This time we needed serious speed reduction so we set 15 inches and 2100 RPM as we descended at 500 FPM. Since we were on HDG mode we could switch fromGPS mode to NAV mode to see the ILS info. It showed we would be just at the glideslope as we made our turn north to the ILS. The GASP light went green just as we started the turn so we lowered the gear. That set us up very nicely for the approach. Visibility improved. We could see the ground but not the runway 8 nm out. We put down first flaps and levelled to let the glideslope come down to us. At 128 KIAS we were in good shap with just a slight crosswind of 14 knots. We pushed the mixture levers full forward. We were still right of the localizer but the wind was helping there. Just as the localizer lined up we saw the light of the runway visual glideslope. At 116 KIAS with one notch of flap we were stabilized 3 miles out. But it was smooth so we dropped the last of the flaps for a slow touchdown. We touched down nicely at 81.07 KIAS and -102 FPM. The rain had stopped. It took 55 minutes from when we taxied out. There were just under 34 gallons in each tank - plenty of fuel in case we had to divert to Huntsville or Birmingham.
Except for the visibility, the ride was not bad for the passengers. We flew over a bunch of mountains. In the East, the Baron is a very good airplane for this sort of job - four passengers on a business trip of up to 300 nm, over Great Lakes or mountain ranges. I would define "the East" as anywhere west of Colorado. But for traveling in the West (west of the eastern edge of Colorado), You need a pressurized and turbocharged twin that will get you above most of the clouds and all of the mountains. For that we will use the Cessna 340 in Part 3.
Tom Goodrick
Re: FLYING PISTON TWINS
« Reply #2 on: Oct 7th, 2007, 6:11pm »
PART 2A SINGLE ENGINE FLIGHT
Before going to the 340, there is something I forgot to do during the last flight - shut down an engine. I decided to take off from CHA and head back toward AVL at 8,000 ft (the same altitude we used coming from there. I would intercept the same track back to CHA and match the cruise condition. Then about half way, I would shut down the right engine. i chose the right so we could make a dangerous turn into the dead engine going to final approach - a situation that has caused many fatalities. I started in clear air intending to turn on Stormy Weather as I made the intercept. There was one surprise. I found the engine running at 68% power in the clear air at 8,000 ft. After the weather was changed, this went down imediately to 61 percent while at the same altitude and power setting. Evidently rain does a job on your available power.
So as we lined up and the autopilot was following the track to KCHA, I set E2 and brought back the mixture, then the prop lever and, finally, the throttle. While fighting the heading on manual control, I dialed in some rudder. That helped. The aircraft rode down the track with a cant to the left but it stayed on course. I was able to maintain 6500 ft and about 140 KIAS. That was good. I don't think the passengers in back enjoyed all the wobbling and weaving. That was bad!
At 33 nm out I turned to 230 degrees to set up the offset for the approach. We started descending but it became obvious that this plane can go down much easier than she can come back up. So make sure you don't get too low. Staying above the glideslope is best. With the rudder trim properly adjusted, I did not have to keep my right foot on the rudder very much. That was nice.
As the turning point to start the approach got closer, I went through a spasm of too low, too high, too fast, too slow. But I eased her around the turn and let the wind blow me into alignment with the localizer. I was well below gear speed but kept the gear up until I could see the runway. This time when 3 miles out, it was raining and they had the moving lights on the threshold drawing us in. That helped. As I got a mile out I was a bit low. I had lowered the gear and first notch of flaps. It took full throttle to get serious about the glideslope. The airspeed was high - 125-130 KIAS for most of final. With the nose up over the runway the crosswind was moving us more left and I had to roll right a bit to hold it on the centerline. But still I ended up touching the left wheel first and then cut power and it became much easier to hold the plane on the centerline as we rolled out. The landing was fast at 101.8 KIAS but smooth at -59 FPM. I held it up just a bit to get rid of some speed, not to make a smooth landing. A firm landing would have been fine - any landing would have been fine!
I taxied close enough so the passengers did not get too wet. They were glad the flight was over. The flying was hard work at times. But it was a lot better than the alternative that would have been the necessity in a single engine aircraft. First, the poor visibility would not have permitted searching for a flat spot to land until too low to do much about it. Secondly, there weren't many flat spots. The few places that were flat, were very wet. We would have drowned in the Tennessee River! At least a twin gives you options and keeps your fate more in your hands. If you screw it up and dump the plane into the ground, that's your fault for not practicing single engine flight. That's my argument to the statisticians who keep saying singles are safer than twins when an engine fails.
Tom Goodrick
Re: FLYING PISTON TWINS
« Reply #3 on: Oct 12th, 2007, 11:53am »
PART 3: PRESSURIZED TWIN
Flying the Cessna 340 from Arcata, CA, to Reno, NV.
To illustrate the utility of the pressurized and turbocharged Cessna 340, we'll fly a payload of two men and two women from Arcata, CA, to Reno,NV. It is a nice flight of about 1 hour. To add visual interest, we will use Fair Weather. This gives us light winds at altitude and a layer of puffy white clouds at about the level of the mountain tops. We'll be flying over 11,000 ft mountains so this is no flight to make in a non-turbocharged aircraft. Without pressurization, we'd have to suck oxygen from a bottle most of the way. But in the 340 we can sit comfortably and breath normally while noting the cabin is at a comfortable altitude.
Our load is 2x(200+160+30). We can't carry a full load of fuel so we left 2 gallons out of each of the main tanks (the 50 gallon wing tip tanks) and left the aux tanks in the wings empty. That gives us 96 gallons, plenty of fuel for one way and even gives us enough fuel for the round trip though we will put in some fuel at Reno out of courtesy and to take advantage of the opportunity (and avoid paying a parking fee). Our weight is 5985 lb (close to max gross) and the CG is at 22%.
We rolled down the runway at 10:16 PDT. We made a manual turn while climbing over the bay but proceeded directly on course. 15 minutes later we were at 19,000 ft and on the GPS Direct Flight Plan. I used 100% power for takeoff, 85% for climb with the RPM at 2412 and reduced throttle for 75% once we leveled at 19,000 ft. That gave us 216 KTAS and 162 KIAS while the wind drift gave us 238 knots ground speed. At 10:37 our ETE was 39 minutes. The ride was nice and smooth. There was only one minor flaw in the operation so far. As we turned onto a path leading to our course during the climb, I turned on the autopilot setting NAV and ALT modes. But it wasn't until I saw our little airplane fly away from the red path that I noticed I had forgotten to flip the panel switch from NAV tracking to GPS tracking. When I changed that switch, the nav computer found a new course intercepting our flight plan course and headed for it.
During the climb we had very little work to do. We left the mixture at full rich and the engines pulled us up at about 1200 fpm most of the way. The autopilot held us on course and leveled us off. We adjusted the throttle for 75% power. That was it. Of course we watched the mountains come at us rather carefully but our climb rate got us above them well before we got close enough for concern.
Our course was nearly due east (099 degrees) and the wind at 19,000 ft was 24 knots from 270 degrees so it was helping us on this leg. It would probably slow us down on the return trip in a few days. I had left the cowl flaps open after reaching cruise altitude because in FS there is no drag penalty. I'll close them and see how much the engines heat up. The CHT's are now 351 F. The OAT shows 8 F so the engines probably will do best with the cowl flaps closed. The TIT's are at 1588. This is good and is staying low because we did not lean any at cruise. We are getting the best power from the turbos at this altitude without risking additional heat. After several minutes, we see the CHT's are not changing. FS is funny about this. Sometimes there is an effect from the cowl flaps and other times there is not. We'll leave them closed until he land s that is considered best for the engines.
In cruise I see 16.22 gph per engine, map is 31.93 inches and the engines are still holding a comfortable 2412 RPM. The power gauge shows 75.16%.
The time is 10:58. our flight time has been 42 minutes. Our ETE is 17 minutes. We are 68 nm out. Our descent to 6,000 ft will take 8.7 minutes during which we will go 26 nm. We'll start down when 36 nm out.
This aircraft is equipped with full height radar altimeter that shows us the ground level from cruise altitude. Most such equipment only works the last 1000 ft. But this will be helpful in our descent. We can correlate altitude clearance with the terrain on the map. At 11:06 it is time to start down. We reduce power to 37% and set -1500 fpm on the A/P. We set 8,000 ft for the first altitude target but we'll be changing that. Right now we see many mountains between us and the airport. It looks like we are aimed at one peak. The cabin altitude was 6000 ft during most of the cruise. It surged to 9,000 ft when we reduced the power. Now it is down to 6,000 ft again so we will ease the throttle back some more. As we are about 10 nm out, we find we can go to 2100 rpm and 15 inches for the descent to pattern altitude. 4 nm out we turn to 160 for a downwind to 34. We are 3000 ft above the sloping terrain from a high ridge toward the airport. We'll head out for a five mile final.
On this aircraft we have both a GASP and a FASP. The FASP turns green first so you can lower flaps to help slow down to gear speed. At 142 KIAS we are extending flaps one. At 136 the GASP is green and we are extending the gear. We start to turn base.
We landed at 11:20 after 62.79 minutes of flight. We burned 32.4 gallons of avgas. The landing was smooth. We used 34L and then had a long taxi to the east side of the field. We headed for Fitch Aviation to park.
« Last Edit: Oct 13th, 2007, 12:21pm by Tom Goodrick »
FLYING PISTON TWINS
« on: Oct 7th, 2007, 3:43pm »
PART 1 INTRODUCTION
We'll start the section on flying twins with the Beech Baron 58. Everybody has this and has probably tried flying it. It is fairly easy to fly if you have worked on the faster singles like the Mooney. Next we'll get into high altitude work with the Cessna 340, a pressurized and turbocharged twin you can get from my web site. But before getting to the specifics of flying each aircraft, there are several basic differences we should discuss between flying twins compared with singles - some obvious and some not.
The only reason most people buy a twin is to have the extra engine when one engine stops running. Many people today fly the large and fast singles over water, at night and in IMC conditions without qualms about engine failures. They can do this because the statistics support the safety of the single engine aircraft of today. At least that has been true many years ago. Today it might not be so great an idea because many of the fast singles are getting old enough to lose some reliability. As a pilot in training with a single-engine airplane, we are taught to be ready to land a single in any reasonable space when the engine quits. On takeoff after the runway disappears behind you and before you reach 1,000 ft, you have no choice but to land dead ahead, trying to miss the hard things. Odds of survival doing this are about 50% at best. Once you are above 1,000 ft you have more choices and can even land on a runway. Your odds of survival increase dramatically to at least 80% although the odds of ending up with an unbent airplane may be 10%. I did it once in a loaded Cessna 150 on a snowy field. We were even able to take off after clearing the carburator ice from the engine. (I was with my instructor but I did all the flying.) Of course, today you can buy an airplane with a parachute. But my experience with parachutes and with parachute landing of heavy items like airplanes makes me doubt the wisdom of it. I'll take an airplane gliding landing any time over a chute. People unlucky enough to land on hard surfaces will probably break their backs with a parachute - if the chute does not oscillate. If it does oscillate and hit on a road or parking lot, they'll break more than their backs. When you fly singles at night or over water, which I have done with plenty of time to consider the possibilities, you realize you will have few choices when the noise stops. IMC (Instrument Meteorological Conditions) is another roll of the dice. As you come out of the overcast, you have a slim chance of being able to glide to a safe landing site. That's why people like to buy twins. They even have a new option to shut down an engine before it is ruined if a temp guage starts looking bad.
In training for flying twins, you learn not to lift off just because the plane is going fast enough so you won't stall. You takeoff when you have enough speed to continue the flight if an engine quits. You practice that condition, first at altitude and later closer to the ground. You must first identify the engine that has quit and then push on the rudder pedal on the opposite side. this is actually an extremely unusual event and very difficult to handle. You are too low and slow to be wallowing around trying to handle the unbalanced thrust. Having an engine shut down at altitude is fairly easy to work with safely. Still, however, it is significant to note that any loss of an engine must be treated as an emergency situation and the pilot must land at the first airport reasonably accessible. Some leeway is granted in this regulation if the pilot feels he has good control of the situation and wants to land at an airport with a long runway. Such airports generally have better repair facilities as well. I demonstrate such a situation where I pass up a few airports to land on a long runway with an ILS because it happens in IMC over mountains.
Twins are more than twice as expensive to operate. Many will carry no more payload than many singles. They all carry a lot more fuel that has to be managed properly during the flight. Keep the fuel balanced or you will have lots of fun when you have to shut down an engine. All twins will have plenty of climb rate when both engines are operating. They have to be designed to get to a flying condition after losing an engine a little after takeoff. This is when the good engine is operating at full power and producing a lot of yaw that must be countered with rudder. Some people say your odds of having an engine quit on takeoff are doubled in a twin. It is still pretty slim. The training program for transition to a twin involved many parctice climbs and other maneuvers on one engine - either engine. According to most statistics, your odds of dying when an engine quits are significantly worse in a twin than in a single. That is because the single pilot is trained to find a good landing site as soon as the engine quits. The twin pilot tries to mess around and get to an airport. He often ends up stalling out as he gets too slow turning final and spins in.
When you fly twins in FS, spend some time flying them with one engine out. In the Baron 58 at max gross weight, the climb rate will be 1750 fpm with both fans turning and only 394 fpm with only one fan. Flying twins on one engine requires patience.
In the US, the FAA requires single-engine aircraft have a landing stall speed below 61 KIAS. Twins do not have this limitation. Designers have given twins higher speed with smaller wings for the weight (ie- higher wing loadings). This is an easy, low-tech approach. But it means you'll have a tough time if both engines quit as when you run out of fuel. It also means every landing and takeoff is a little faster than in a single. Thus it requires a little better pilot skill level.
When flying twins, it is usually more important to learn and to watch all the required speeds and procedures. To lift off well, many twins require one notch of flaps. Thus, as soon as you lift off, you are busy raising the gear and the flaps. You must also stay low over the runway until you have VMC which is the minimum control airspeed at which the rudder has enough power to keep you straight if one engine is at full power while the other engine is at zero power. This number is not easily found for many aircraft so I use the rule of thumb that VMC is 10% above clean stall speed.
Be aware that there will generally be more of a trade-off to make between payload and fuel because the fuel is a larger percentage of the max gross weight in many cases. In many twins, all the back seats have to be empty if you fill the tanks. This means you have to figure the fuel burn for a trip and carry only enough for the trip (or for one leg of the trip) plus 45 minutes of extra cruise to get to a new landing site if the first does not work out. Another complicating factor is that many twins have a max landing weight (MLW) that is significantly less than the max takeoff weight (MTOW). Thus for short trips with big loads, you may have to keep the fuel load low to be under MLW when you arrive at the destination.
Twins cruise high and fast. This will require some planning when you get near the destination - or even within 50 nm of it. You will have to know the safe speed for extending gear, and the safe speed for extending flaps. The general power setting that works for getting down from cruise to an altitude for the approach to the area near the airport is 15 inches MP and 2100 RPM. in many cases this will get you down close to gear speed or flaps speed shortly after you level off near the airport. It is customary to put the gear down at that time. Note that in some cases, the flaps can go to the first notch at a higher speed than the gear can be extended. In this case the flaps go out first and help slow the plane for gear extension. In most cases both the first notch of flaps and the gear will be extended as you start down final approach. In unpressurized aircraft like the Baron, you must keep the descent rate no greater than 500 fpm and manage the mixture to keep enough power.
Twin pilots are generally a lot busier than single pilots. They have twice as many engine gauges to look at, twice as many levers to push or pull and twice as many switches plus a few more like synchrophasers. Fuel management becomes an issue even in FS. I use the Baron power quadrant with the fuel switches on all piston twins. With many aircraft as you fly, one engine takes more of the fuel than the other. You have to watch this and switch the fuel to cross-feed off the low tank to keep the tanks balanced. I have flown on many twins where the pilots had trouble synchonizing the engines. This can drive you nuts, hearing and feeling the out of synch vibrations. In FS we don't have much of a problem. If you get one engine slow, just shove both throttles forward and draw them back as one.
The fact that you must fly final about 20 knots faster than in singles is another issue. Indeed 20 knots is about the difference in final approach speed for each level of sophistication: 70 KIAS for singles, 90 KIAS for twins, 110 KIAS for turboprops and 130 KIAS for bizjets. You have to handle the power changes, trim changes, gear and flaps as the runway rushes at you faster and faster. That is why I strongly urge people to work their way up through the different levels of difficulty, getting very profficient at one before moving up to the next. Unfortunately, I keep getting rusty at the more challenging aircraft and have to re-learn the procedures all the time when I go back to them. i may have to adopt a rule such as:
Fly jets every Monday and Tuesday, turboprops every Wednesday, piston twins on Thursday, singles on Friday and anything, including helicopters on weekends!
That would help maintain proficiency!
« Last Edit: Oct 8th, 2007, 12:03am by Tom Goodrick »
Tom Goodrick
Re: FLYING PISTON TWINS
« Reply #1 on: Oct 7th, 2007, 6:09pm »
FLYING TWINS PART 2
BARON 58 FROM KCHA TO KAVL AND BACK
We'll give the Baron a typical job. We'll fly empty (one pilot) from Chattanooga TN to Ashville NC and then pick up 4 passengers with luggage for the return flight. We check the amount of fuel that can be carried with the four pax figuring 4(180+20)+220 for the pilot (me). Then we add less than an hours' fuel for the trip out (20 gal) and start with that fuel but with an empty cabin. This will give us max fuel coming back.
At the start we load 59 gallons per side. Now we have 118 gal, 4838 lb gross weight. We enter a GPS direct flight to KAVL. We check cowl flaps - open. Check fuel switches - both up. Fuel Pumps - High. We set the autopilot - HDG 020, ALT 7500 ft. There is no wind so takeoff will be made on runway 2, which takes us away from the city. We switch on the beacon and the strobes. We verify that the flight plan is in the nav computer. We set the trim at 7 degrees for takeoff. Flaps are up. We taxi to runway 2. We stop at 2 and note it is 13:03. Time to go.
We swing into place on runway 2 and are cleared for takeoff. The throttles go full forward. 90 KIAS comes quickly and we rotate and fly away. Gear comes up. At 1000 ft above ground we set the autopilot ON and set the climb rate for 1200 fpm. Soon after that we turn to 090 to intercept our course. We reduce the RPM to 2500 and climb at about 72%. At 5,000 ft we lean for max fuel flow. We see 75% power briefly climbing through 6300 ft for our cruise altitude of 7500. All the engine numbers are in the green - literally - meaning all is okay. At 7500 ft the autopilot levels us and we lean once again for best power (max fuel flow). The power turns out to be 70%. That's the best we can do at this altitude. We continue on a heading of 090 even though that shows convergence with our flight plan path about 20 miles ahead. This is a VFR flight. If it were an IFR flight, we could converge earlier. It is time to enjoy the great scenery. The nav computer says we have about 30 minutes.
I switched the fuel pumps to low during cruise. The ground speed (same as true airspeed with no wind) was steady at 202 knots. Airspeed was 182 KIAS. The scenery now includes mountains and rivers - very picturesque. We adjust the ILS arrow to point to 340, the runway heading for our landing. We will soon deviate from the straight course to the airport to get in position for a descent along the direction of 340 which will keep us in the middle of a valley leading to the airport. Some of the mountain peaks are over 5500 ft in the area. The airport is at about 2200 ft msl. There are no weather problems on this trip because we have turned the weather OFF. We'll get hit with some storms on the way back.
Okay, we are 34 nm out. I am going to turn 20 degrees right of our course to get a good offset for the descent. This worked fine. At 10 nm on a diagonal from the airport, I was ready to start the descent. The high rocks had cleared from the circular path I wanted to take getting lined up with the runway for a straight-in final from 5 nm out. This is a case where you must use the GPS map in relief mode to see where the high rocks are. The radar altimeter is very useful too and helps you interpret the elevations shown on the relief map. I pulled the throttle back to 18 inches and then the RPM back to 2100. I shut off the autopilot and begane the circular descent. Soon it was evident i need to slow more and descend a bit steeper so I pulled the throttles back to 15 inches. I ended up too high and too fast even after slipping a bit so I turned left from the runway direction and did a gentle 360. There was no traffic. (I never turned that on for this flight.) During the turn, which was well inside the valley, I slowed enough to get a green light for the gear and i knew that when the gear can go down, the first notch of flaps can go out. When the runway came around again I was about 2 nm out and just under the visual glideslope at 111 KIAS as I let down full flaps. Over the fence I cut the power to idle. The landing was nice at 77.22 KIAS and -150 FPM. At 14:53 we were parked. (We had crossed a time line just after leaving Chattanooga. I parked and headed for the Berry Patch Cafe for pie and coffee and to meet the passengers. I didn't notice the rain clouds forming just west of the peaks to the west and moving our way.
I had time to eat my pie, sip my coffee, meet the passengers and get them into the plane before the deluge hit. The right seat got pretty wet as I climbed in. I started the engines and let them idle while I filed the flight plan back to Chattanooga. The fuel was down to 45.7 gallons per side - just right for the increased load. The gross weight was now 5479 lbs and the CG was not at 29.05% MAC. This would be quite a different aircraft than the one I flew over. As the rain hit the wind was gusting quite a bit. The heavier weight would make for a steadier ride in the gusty wind. The wind was from the north so we would use runway 34. I set the autopilot for 340 and 8000 ft cruise altitude.
Fuel selectors up, mixture and prop forward, autopilot set but not ON, fuel pumps on High, strobes and beacon on for taxi, fuel good, weight and CG good. We were ready to taxi. Trim went to 7 degrees as we taxied out at 16:00. Visibility was good for takeoff. We could see most of the runway! At 400 feet we turned on the autopilot. The mountains on either side were in the haze, rain and clouds so we stayed on runway heading until reaching cruise altitude of 8,000 ft. We had been climbing at 1200 fpm but that was too much in the rain. We reduced that to 800 fpm and adjusted the mixture at 6,000 ft.as the airspeed continued to drop we reduced the climb rate to 200 fpm at 7500 ft. Then we started to get more airspeed. At 8,000 ft we had 105 KIAS and we turned to 220 degrees to get back on our course. With the wind at 19 knots from 90 degrees we had a nice groundspeed of 207 knots. But we could only gte 61 % power so our indicated airspeed was only 168 KIAS. We were still in the rain and the clouds (using "Stormy Weather"). At 8,000 ft our radar altimeter read 2,000 ft as a nasty-looking peak passed nearby on our left. As we turned onto course for Chattanooga, the groundspeed increased to 215 knots with the wind more directly on our tail (wind 90 dgrees and course now 265 degrees). There was probably some pretty scenery underneath us but we couldn't see it in the clouds and rain. Leaning produced only 14.40 gph per side for 61.25% power.
About halfway there the rain stopped but we were still in clouds so we set the radio for the ILS to runway 2 at KCHA (108.3 and 019 degrees). 40 miles out we made a jog to the south of course to get the offset for the turn onto the approach. We turned to 232 degrees. It started to get lighter out and we could see the ground far below (5,000 ft below) for a brief moment and then the rain started up again and it got dark. At 33 nm out we were past the tall mountains so we could descend to 6,000 ft. We reduced power to 15 inches and 2300 rpms (30.9%). At 25 nm out we could turn to 260 degrees. This put us on a tangent to the 10 mile circle around KCHA. At 6000 ft we leveled and brought the power up to 60% with an increase in the manifold pressure to 22 inches. With the wind drift we were closing fast on the circle so we continued down to 4,000 ft. This time we needed serious speed reduction so we set 15 inches and 2100 RPM as we descended at 500 FPM. Since we were on HDG mode we could switch fromGPS mode to NAV mode to see the ILS info. It showed we would be just at the glideslope as we made our turn north to the ILS. The GASP light went green just as we started the turn so we lowered the gear. That set us up very nicely for the approach. Visibility improved. We could see the ground but not the runway 8 nm out. We put down first flaps and levelled to let the glideslope come down to us. At 128 KIAS we were in good shap with just a slight crosswind of 14 knots. We pushed the mixture levers full forward. We were still right of the localizer but the wind was helping there. Just as the localizer lined up we saw the light of the runway visual glideslope. At 116 KIAS with one notch of flap we were stabilized 3 miles out. But it was smooth so we dropped the last of the flaps for a slow touchdown. We touched down nicely at 81.07 KIAS and -102 FPM. The rain had stopped. It took 55 minutes from when we taxied out. There were just under 34 gallons in each tank - plenty of fuel in case we had to divert to Huntsville or Birmingham.
Except for the visibility, the ride was not bad for the passengers. We flew over a bunch of mountains. In the East, the Baron is a very good airplane for this sort of job - four passengers on a business trip of up to 300 nm, over Great Lakes or mountain ranges. I would define "the East" as anywhere west of Colorado. But for traveling in the West (west of the eastern edge of Colorado), You need a pressurized and turbocharged twin that will get you above most of the clouds and all of the mountains. For that we will use the Cessna 340 in Part 3.
Tom Goodrick
Re: FLYING PISTON TWINS
« Reply #2 on: Oct 7th, 2007, 6:11pm »
PART 2A SINGLE ENGINE FLIGHT
Before going to the 340, there is something I forgot to do during the last flight - shut down an engine. I decided to take off from CHA and head back toward AVL at 8,000 ft (the same altitude we used coming from there. I would intercept the same track back to CHA and match the cruise condition. Then about half way, I would shut down the right engine. i chose the right so we could make a dangerous turn into the dead engine going to final approach - a situation that has caused many fatalities. I started in clear air intending to turn on Stormy Weather as I made the intercept. There was one surprise. I found the engine running at 68% power in the clear air at 8,000 ft. After the weather was changed, this went down imediately to 61 percent while at the same altitude and power setting. Evidently rain does a job on your available power.
So as we lined up and the autopilot was following the track to KCHA, I set E2 and brought back the mixture, then the prop lever and, finally, the throttle. While fighting the heading on manual control, I dialed in some rudder. That helped. The aircraft rode down the track with a cant to the left but it stayed on course. I was able to maintain 6500 ft and about 140 KIAS. That was good. I don't think the passengers in back enjoyed all the wobbling and weaving. That was bad!
At 33 nm out I turned to 230 degrees to set up the offset for the approach. We started descending but it became obvious that this plane can go down much easier than she can come back up. So make sure you don't get too low. Staying above the glideslope is best. With the rudder trim properly adjusted, I did not have to keep my right foot on the rudder very much. That was nice.
As the turning point to start the approach got closer, I went through a spasm of too low, too high, too fast, too slow. But I eased her around the turn and let the wind blow me into alignment with the localizer. I was well below gear speed but kept the gear up until I could see the runway. This time when 3 miles out, it was raining and they had the moving lights on the threshold drawing us in. That helped. As I got a mile out I was a bit low. I had lowered the gear and first notch of flaps. It took full throttle to get serious about the glideslope. The airspeed was high - 125-130 KIAS for most of final. With the nose up over the runway the crosswind was moving us more left and I had to roll right a bit to hold it on the centerline. But still I ended up touching the left wheel first and then cut power and it became much easier to hold the plane on the centerline as we rolled out. The landing was fast at 101.8 KIAS but smooth at -59 FPM. I held it up just a bit to get rid of some speed, not to make a smooth landing. A firm landing would have been fine - any landing would have been fine!
I taxied close enough so the passengers did not get too wet. They were glad the flight was over. The flying was hard work at times. But it was a lot better than the alternative that would have been the necessity in a single engine aircraft. First, the poor visibility would not have permitted searching for a flat spot to land until too low to do much about it. Secondly, there weren't many flat spots. The few places that were flat, were very wet. We would have drowned in the Tennessee River! At least a twin gives you options and keeps your fate more in your hands. If you screw it up and dump the plane into the ground, that's your fault for not practicing single engine flight. That's my argument to the statisticians who keep saying singles are safer than twins when an engine fails.
Tom Goodrick
Re: FLYING PISTON TWINS
« Reply #3 on: Oct 12th, 2007, 11:53am »
PART 3: PRESSURIZED TWIN
Flying the Cessna 340 from Arcata, CA, to Reno, NV.
To illustrate the utility of the pressurized and turbocharged Cessna 340, we'll fly a payload of two men and two women from Arcata, CA, to Reno,NV. It is a nice flight of about 1 hour. To add visual interest, we will use Fair Weather. This gives us light winds at altitude and a layer of puffy white clouds at about the level of the mountain tops. We'll be flying over 11,000 ft mountains so this is no flight to make in a non-turbocharged aircraft. Without pressurization, we'd have to suck oxygen from a bottle most of the way. But in the 340 we can sit comfortably and breath normally while noting the cabin is at a comfortable altitude.
Our load is 2x(200+160+30). We can't carry a full load of fuel so we left 2 gallons out of each of the main tanks (the 50 gallon wing tip tanks) and left the aux tanks in the wings empty. That gives us 96 gallons, plenty of fuel for one way and even gives us enough fuel for the round trip though we will put in some fuel at Reno out of courtesy and to take advantage of the opportunity (and avoid paying a parking fee). Our weight is 5985 lb (close to max gross) and the CG is at 22%.
We rolled down the runway at 10:16 PDT. We made a manual turn while climbing over the bay but proceeded directly on course. 15 minutes later we were at 19,000 ft and on the GPS Direct Flight Plan. I used 100% power for takeoff, 85% for climb with the RPM at 2412 and reduced throttle for 75% once we leveled at 19,000 ft. That gave us 216 KTAS and 162 KIAS while the wind drift gave us 238 knots ground speed. At 10:37 our ETE was 39 minutes. The ride was nice and smooth. There was only one minor flaw in the operation so far. As we turned onto a path leading to our course during the climb, I turned on the autopilot setting NAV and ALT modes. But it wasn't until I saw our little airplane fly away from the red path that I noticed I had forgotten to flip the panel switch from NAV tracking to GPS tracking. When I changed that switch, the nav computer found a new course intercepting our flight plan course and headed for it.
During the climb we had very little work to do. We left the mixture at full rich and the engines pulled us up at about 1200 fpm most of the way. The autopilot held us on course and leveled us off. We adjusted the throttle for 75% power. That was it. Of course we watched the mountains come at us rather carefully but our climb rate got us above them well before we got close enough for concern.
Our course was nearly due east (099 degrees) and the wind at 19,000 ft was 24 knots from 270 degrees so it was helping us on this leg. It would probably slow us down on the return trip in a few days. I had left the cowl flaps open after reaching cruise altitude because in FS there is no drag penalty. I'll close them and see how much the engines heat up. The CHT's are now 351 F. The OAT shows 8 F so the engines probably will do best with the cowl flaps closed. The TIT's are at 1588. This is good and is staying low because we did not lean any at cruise. We are getting the best power from the turbos at this altitude without risking additional heat. After several minutes, we see the CHT's are not changing. FS is funny about this. Sometimes there is an effect from the cowl flaps and other times there is not. We'll leave them closed until he land s that is considered best for the engines.
In cruise I see 16.22 gph per engine, map is 31.93 inches and the engines are still holding a comfortable 2412 RPM. The power gauge shows 75.16%.
The time is 10:58. our flight time has been 42 minutes. Our ETE is 17 minutes. We are 68 nm out. Our descent to 6,000 ft will take 8.7 minutes during which we will go 26 nm. We'll start down when 36 nm out.
This aircraft is equipped with full height radar altimeter that shows us the ground level from cruise altitude. Most such equipment only works the last 1000 ft. But this will be helpful in our descent. We can correlate altitude clearance with the terrain on the map. At 11:06 it is time to start down. We reduce power to 37% and set -1500 fpm on the A/P. We set 8,000 ft for the first altitude target but we'll be changing that. Right now we see many mountains between us and the airport. It looks like we are aimed at one peak. The cabin altitude was 6000 ft during most of the cruise. It surged to 9,000 ft when we reduced the power. Now it is down to 6,000 ft again so we will ease the throttle back some more. As we are about 10 nm out, we find we can go to 2100 rpm and 15 inches for the descent to pattern altitude. 4 nm out we turn to 160 for a downwind to 34. We are 3000 ft above the sloping terrain from a high ridge toward the airport. We'll head out for a five mile final.
On this aircraft we have both a GASP and a FASP. The FASP turns green first so you can lower flaps to help slow down to gear speed. At 142 KIAS we are extending flaps one. At 136 the GASP is green and we are extending the gear. We start to turn base.
We landed at 11:20 after 62.79 minutes of flight. We burned 32.4 gallons of avgas. The landing was smooth. We used 34L and then had a long taxi to the east side of the field. We headed for Fitch Aviation to park.
« Last Edit: Oct 13th, 2007, 12:21pm by Tom Goodrick »