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Post by dirtydog1006 on Nov 17, 2010 15:02:04 GMT -5
Following some on-line advice for landing the default 172, I am at 75KIAS with one 'notch' of flaps at the FAF. The advice then gets thin. So I come to the experts.
I cruise down the glideslope and, when the time seems right, I pop the second notch of flaps. I've been triming to maintain the 75KIAS. But should I?
Over the fence (I always wanted to say that) I go to full flaps and sort of let the speed degrade a bit. Should I maintain 75 at this point?
Somehow, often, I end up touching down in the low to mid 50s KIAS, and feel bad if the FPM is over -60 or so. Are these reasonable figures?
I tried to make this a reply to Tom's LANDING article, but somehow could not. SOrry for the new-thread approach.
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Ed Burke
Member
Healthy living is fine, but it's having fun that keeps us going!
Posts: 433
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Post by Ed Burke on Nov 17, 2010 16:37:39 GMT -5
Hi DD, I have never landed a 172 but my missus says what you are doing is fine for still air but you need to keep the speed a tad higher in rough or cross wind conditions especially at touch down. I guess she is saying "Fly it on"
Ed
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Post by flaminghotsauce on Nov 19, 2010 13:03:11 GMT -5
Are you talking a true IFR approach to an ILS landing? If you can see the runway, you can adjust flaps to best suit the situation. Foggy days where you pop out at minimums might not have much wind and would probably require more flaps, but if you have a windy approach, you might land with only one notch of flaps.
I was taught to approach at 70 kts. On a typical VFR circuit, I pull power even with the end of the runway on downwind, hold the nose up until flap range, enter on notch of flaps and trim for about 475 fpm. Turn base and drop a second notch, and at this point I would be trimming for 70 kts, and usually never needed more flaps than this. Turn final, hold 70 kts until over the fence, pull power and I never looked at the airspeed from that point on.
But if you're talking straight it approach on the ILS, your figures are probably close. Although from the FAF, we would go 90 kts so we could accurately time the approach. If you're not timing and there's not a 737 coming behind you, 75 kts will work.
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Post by louross on Nov 19, 2010 16:08:54 GMT -5
Haven't flown a 172 since 1968. (or was it 67, let's see, ...) Anyway, flying VFR pattern I pretty well followed the way flaminghotsauce does it. However, on a straight in approach, like from the FAF, I did it totally different. I usually didn't use flaps in a 150 or 172. Used flaps in a 182. I really didn't see the need for flaps except for instructing in the use of, playing, or some other situation not "normal". To me those airplanes don't need flaps when flying in and out of typical airports. Anyway, flap speed at the FAF to touchdown has got to be a loooong flight. I crossed the FAF at cruise speed and then pulled the throttle back and it would slow approaching the runway, then no problem making the turn-off. I don't remember ever actually making an ILS in a 172 under actual conditions, just simulated. lr.
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Post by Tom Goodrick on Nov 19, 2010 23:17:42 GMT -5
I like Flaming's 70 KIAS. I learned to fly the real 172 in the day we used mph. 70 KIAS is 80 mph indicated which was a main number I learned for use in the 172. We did slow a little more over the fence on calm days with full flaps. I was taught to use full flaps when the winds were light. We had trees near the runway and steep approaches were best. But in windy conditions we held 80 mph down to the runway with only one notch of flaps.
Before I say much more, I'd better read what I wrote about landing in the sim before saying anything else.
A key objective in any landing is to get the wheels firmly on the ground with control of the aircraft. You don't want to get in the habit of beating the landing gauge by holding off until each wheel can kiss the ground. Given enough float time, you'll get in trouble.
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Post by Tom Goodrick on Nov 20, 2010 10:15:10 GMT -5
The official Cessna 1968 Owner's Manual only mentions 69 mph as the speed to use with 40 degree flaps for a short field landing. But, in general, 170 KIAS or 180 mph sound good.
Anyone who is curious about touchdown speeds can obtain and use my landing speed gauge. You must display it at some time during the flight to "arm" it. Then, whether visible or not, it captures the airspeed and vertical rate at the instant the main wheels touch. It must be displayed and read after the touchdown but before parking the aircraft (when indicated values go to zero). During flight it gives an accurate digital indication of speeds when turned on (after a few seconds if the wheels are still spinning).
If you didn't get one from my old web site, just send me an email. Examples of its use can be seen on my first Landings article in this section. Since we don't feel the bump, I don't know how else sim pilots can rate their landings.
In regard to the question posed above which may have questioned landing numbers, I'd feel real good about any lvertical rate at touchdown better than -60 fpm. But within 60 fpm either side of -120 is good and definately acceptable. I have just been doing a number of landings in a 707 with bad FD and was happy to see -500.
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Post by Tom Goodrick on Nov 20, 2010 12:48:48 GMT -5
Below is a section of my landing log file for FS9 on the laptop computer. The average vertical rate for the first 48 flights was -203 fpm. DATE AIRCRAFT AIRPORT KIAS FPM WT CG REMARKS 10/24/10 AC500 HSV 76.74 -69 5545 20.36 From HOU in 170 min, Dyn RW 10/26/10 AC500 HSV 66.27 -150 5377 26.01 RW STRONG WINDS STORMS 10/29/10 B C90B HSV 110.3 -140 9739 16.56 RW STRONG WINDS 10/29/10 B7374 JFK 146.2 -126 127935 19.53 RW STRONG WINDS USED 31L 10/29/10 B A36 CDW 75 -179 3630 23 RW STRONG WINDS 10/30/10 B7374 SFO 120.4 -66 128055 19.53 CLEAR PRACTICE 10/30/10 B B58P MRY 76.3 -195 4634 16 RW 10/30/10 B B58 DVO 80.83 -288 4901 17.11 NOVATO IN RAIN 10/30/10 B A36 DVO 74.64 -130 3368 22.53 SAME 10/30/10 B A36 DVO 67.17 -159 3368 22.53 SAME 10/30/10 B V35B DVO 71.39 -334 2857 26.21 SAME 10/30/10 C 340 DVO 74.28 -436 5579 27.49 SAME 10/30/10 AC500 DVO 68.97 -226 5366 25.97 SAME 11/02/10 PMERIDIAN HSV 78.41 -33 4808 25.41 RW110210 WIND 120 AT 11 11/03/10 PMERIDIAN HSV 77.92 -55 4693 25.42 RW110210 WIND 120 AT 11 As usual the formatting from my spreadsheet was fine even copied into Notepad. But this Forum screws it all up. I did not want to burden you with all the data which pertained mainly to checking planes after transferring them to the laptop. For the future I have added columns for flap settings and flight time. I have been using a lot of RW (Real Weather) and DRW (Dynamic Real Weather). When using RW, I often pop over to my destination and chck the visibility and wind (to get the landing runway). But with DRW you don't know what the conditions will be until you get there. The screen photo above shows my landing on 36R at HSV of the Aero Commander 500 in a strong, gusty crosswind, RW on 10/26 when we had several tornadoes in the area. At 3000 ft on "downwind" the wind was at 38 knots, veering from 270 through 180 to 30 degrees. At the landing it was 15 kts from 315. On short final I noticed 13 kts from 245. The landing speeds were 89.28 KIAS, -225 fpm. Note the crab angle. In FS you don't have to worry about touching down in a crab as the wheels have very little lateral friction. That is the wind sock just off the left wing tip.
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Post by dirtydog1006 on Nov 30, 2010 15:49:55 GMT -5
Thanks for all the great advice! It is turning out as I suspected: Beginners want rules, old-timers have 10,000 special cases in their heads. Landing ze airplace is no different. I was relieved to see that decent rates as high as -180 would be acceptable. I was beating myself up for anything over -100 (a figure I got in my head from somewhere.) Even though from the outside view, on the instant replay, the TD looked fine. Again, Thanks and Happy Holidays to all!
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Post by Tom Goodrick on Nov 30, 2010 20:16:19 GMT -5
Two things - 1) Its hard to cover all possibilities with rules. 2) Knowing the theory can get you through a lot of unxpected situations for which "rules" hsve not been devised.
It probably is true that people break airplanes during the landing sequence more than any other aspect of flying. A hard landing is one way. -300 fpm is the limit to which most light aircraft landing gear is designed. That does not mean you'd be comfortable or happy with such a bump. Large aircraft such as heavier multi-engine or airline-type aircraft have gear designed to take higher loads. -600 fpm is a typical limit for airliners. Their passengers feel less of a bump at -600 fpm than those in a small plane feel at -300 fpm. The difference is the airliner would wear out its gear making several landings per day if the bumps were frequently up near -600 fpm.
But it is also true that a common cause of landing accidents with small aircraft is pilots holding off until they can get a super soft touchdown. While they re getting lower and slower, they are losing some control needed when a gust picks them up and rolls or yaws them a little.
Get into the habit of flying your plane directly to the runway with just a small flare. Get it on the ground with good control and maintain control during the roll out.
The theory in regard to landing shas to do with an aircraft's stall characteristics and its handling in slow flight. Consider the basics. A cruising aircraft needs to descend and land to complete the flight. To land, it needs to slow down. Slowing down while descending is a lot harder than slowing down in level flight. The pilot should reduce power in level flight to slow down somewhat before descending. If he levels off for a while before begining the final approach, he needs to keep the power low. Flaps should be extended a little at a time as they upset your speed and attitude. Begin with the first flaps before starting final. This leads to a stable approach where you don't get upset at critical times when low and slow. Ad speed and use less flaps if the wind is high and gusty. Know your sight picture in the airplane when over the runway and settling in. Do not disturb it in any way before the wheels are on the runway. practice will give you a sense of the right partial-power glide for final. Speed on fnal should be 1.3 times the stall speed in the landing configuration. If you don't know the stall speeds for each flap setting, better find out. That figure of 1.3 is supposed to allow for gusty wind. Sometimes you might consider padding it.
FS does not teach proper crosswind technique. Yu can land in a yawed condition, as much as 40 degrees to the runway and nothing bad will happen in FS. But bad things would happen in the real world if you tried that. In the real world, you would try to reduce the yaw before touchdown. One way is to fly straight along the centerline while lowereing the upwind wing to cancel lateral drift. You touch down on the upwind wheel first and then the downwind wheel.
Power is often used slightly during the landing approach to reduce the vertical rate. How much power you add is the trick to be learned. It depends on the power and type of engine. This works better than using the stick in many cases. Keep your attitude steady.
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Post by Tom Goodrick on Dec 1, 2010 10:07:30 GMT -5
One great thing to do in FS, that cannot be done in the real world, is to get over the airport at about 3000 ft AGL and then shut off the engine. The 172 is a great airplane for this but so are most singles and light twins. You need to know you best glide airspeed (80 mph by the book, 70 KIAS) and hold very close to that all the way down. Being over the airport means you can obviously glide to it. But, that is not so easy beacuse you must go away a little to make your final approach. Of course, with no power, you cannot fly a normal glideslope. Your approach must be steep and there is only a moderate amount of latitude in performing your tranistion from steep glide to flare. Do this with, and without, a wind. In theory, you could glide 5 miles in the 172 after losing an engine at 3000 ft. But that is in a straight line with no wind and making no mistakes. Two miles would be the limit for most people.
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