Tom's Blog Two

[Tom Goodrick]

This may be a good time to start a second blog so you don't have to look through 6 pages.

Excuse me while I get out several soap boxes and stack them on top of each other. I have something to proclaim.

In the September issue of FLYING, Peter Garrison, the "tech editor" (who succeeded J Mac Mc Clellen ay that post) has written an article about airfoils. The gist is that we don't need them on our airplanes anymore. hed escribes the history of airfoils, but, he misses THE POINT. He is trained in journalism with only some rough self-training in aerodynamics. I have found fault on technical aspects of many of his articles. This is not too bad in some ways. Much of it is even true. But he misses THE POINT.

It is true that, as he says, wings made from flat plates can fly. We have all made paper airplanes. They fly and can be made to fly in the same manner as other airplanes by adding control surfaces. A wing does not have to have a thick airfoil to fly. But it certainly does help in many ways. It makes the wing a whole lot friendlier at stall.

But what is THE POINT he missed? It is the "Kutta condition" which may be stated:

"A body with a charp trailing edge which is moving through a fluid will create circulation of sufficient strength to hold the rear stagnation point at the trailing edge."

[From Foundations of Aerodynamics by Kuethe and Schetzer, John Wiley & Sons]

Flow fields may be analysed as a sum of different terms. You start with uniform flow - every air molecule moving at the same speed from left to right. Then you can add a circulation feature where air flows around a body in a clockwise fashion combined with that left-right uniform flow. Adding the two terms at various poiints around the object, you see that air moves slower past the bottom than orver the top. When air moves slowly past a surface, it exerts more pressure on that surface than if it moves quickly. So air pushes in on the body from both the upper surface and from the lower surface. If the push from underneath is greater, you see a lifting force.

So back in the days before people had much practical experience with flying objects, mathematicians were showing that circulation around a body in a flow would give it lift - a force perpendicular to the direction of airflow. When they looked at plots of the total airflow (velocity values at all points around the body, it began to look like the body with circulation was flying at an angle of attack.

Garrison misses the aspect of how early aerodynamicists came up with airfoil shapes. The were using math with a device called a potential function that enabled them to combine uniform flow with circulation and with several other proerties to map a circle in an arbitrary and contrived math space into a shape in real space that looked like what we call an airfoil. Its exact shape related to the flow properties they were looking for. They certainly did not conjure the shapes out of thin air!

The point at the trailing edge makes the upper surface flow get together smoothly with the lower surface flow. Without this things get messy and you cannot sustain lift reliably. You get unsteady forces. If you were to try to get a thick brick to fly, it would not develop a steady force at any angle of attack. I have seen windtunnel tests of such objects, intended to show how large cargo payloads behave when exiting the rear ramp of a flying aircraft (to be recovered by a parachute). They do not fly well unless you introduce the edge of a bottom platform. The edge of that platform can satisfy the Kutta Condition.

There has been a gentleman designing model aircraft for FS who did not know about this theory. He made great models based on three-view drawings but he thought all tail surfaces ended in flat backs like bricks. I told him that looked bad and would bother many pilots who know better. I suggested he use plastic models as the bases for his designs. (I did that for the Bonanza.) he refused to make any changes so I quit corresponding with him and deleted his aircraft.

In the article, Peter Garrison says that the X-15 had bluff trailing edges on its tail surfaces. I have seen a mock-up of the X-15 but thought some details were left undone. If that is true, it is the reason that every landing of the X-15 was a partially-controlled crash. That aircraft had no need to takeoff so its only flight regime was supersonic and hypersonic until just before the landing.

Aircraft that must operate a significant amount of time at subsonic speeds must have control surfaces that have airfoils with sharp trailing edges so that the surfaces can develop lift. In all subsonic phases of flight, the tail provides control of airspeed. Without very good control of airspeed, an airplane would be uncontrollable. This includes the Space Shuttle Orbiter which must finely manage airspeed during final approach as it goes from 400 KIAS to about 200 KIAS at landing.

In his article, Garrison really does not have much of a conclusion. he shows the standard chart of lift, drag and moment coefficients for a NACA 23012 airfoil without mentioning that this has been used on Beechcraft aircraft for many years. (Note the negative pitching moment Flaps would add camber and increase the negative value of the pitching moment - something we discussed in regard to landing attitude for a view over the panel.)

[Ed Burke]

The flying surfaces of the X-15 were conventional albeit on the very thin side. The only surface that was radical was the trailing edge of the rudder which was truncated and as aerodynamic as the rear of a refrigerator. I'm thinking that at hypersonic speed the airflow had left the scene at the leading edge and the strong broad section of the rudder was a handy place to mount the air brakes. I wonder if these were differential?

Ed

[Tom Goodrick]

I can understand that. In those days the aerothermal effects of hypersonic flow were not well understood. Indeed the X-15 program contributed greatly to the knowledge base. They probably thought the sharp trailing edge would get too hot. Now we have materials that can handle that situation. The new (30 years old) carbon-carbon material is used on the Shuttle at hot spots.

[Tom Goodrick]

So now the wife bought a new desktop computer with a screaming Celeron cpu, 2 GB ram and a 160 GB drive. It even has geforce graphics. It is for her games.

She objected to my running programs on the laptop that was a joint gift we gave ourselves for Christmas. So much for togetherness. I was not even using it anymore.

[Ed Burke]

I wouldn't dare tread that path. Nicole has her own desktop setup, quite a sprightly unit and that keeps her off the streets with her amazing email flow and the odd graphics requirement that comes with some of the fancy attachments.

I have my hack desktop machine which is currently doing the sim thing too, while over in the cupboard is my gee-wizz simmer. It has been a gee-fizzer and has only just come back from the repair man who has managed to get it fired up with its three screens working and he reckons it is a blast. Too busy with other things to get it set up but, soon.

Meanwhile I dipped into my moth infested purse and bought a life membership of FSGenesis. Verygood indeed and I have no regrets. Their worldwide mesh makes flying so much better, good stuff. I am currently wandering north along the Appalachians and enjoying the scenery very much. I guess a landclass addon would improve it even more but landclass seems to be only available in small area packages.

Anyway, a heads down attitude seems wise in Madison right now, good luck.

Ed

[Tom Goodrick]

We have had several unexpected expenses lately, buying a new car being one of them and selling the 17-year-old car for only $150 being another. So I was surprized when the wife came up with this idea of a new desktop model for herself. I need a new keyboard before I can do much more music recording. The kittens from the stray momma cat we have been raising will now cost us $200 to enable a vet to "give" them away. The momma has cost us $80 and will cost $150 more before we can give her away (that may not even be possible).

Anyway, on the list of things to get is a flying wheel/pedal system for USB for the laptop. I have already a driving wheel/pedal system for it.

[flaminghotsauce]

So are you going to FS9 that lappy?

[Tom Goodrick]

No, I won't fly on the laptop. There's no reason to. Ol' Betsy here does just fine for FS9 and several other programs. I may have to stop using it to access this Forum because I keep getting pop-up ads for Flash that are very annoying. I had Flash on this computer many years ago. (It runs Win 98). But once when I answered one of these ads by saying "Yes, give me your upgrade" it crashed and has crashed ever since when I try to do anything with flash. i managed to get it to a state where most web sites detect that I don't have flash. That enables me to still go to some sites like Amazon from which I order stuff. But now the laptop does the heavy-duty surfing.

Well, here on the second Saturday of College Football Season, my wretched excess in luxury caught up with me. For a couple years I have been enjoying High Definition LCD TV on a 40 inch screen at 780 pixels for most sports, movie and broadcast stations. It is truly incredible. But lately when I sit back towatch TV I take my glasses off. pretty dumb - huh?

Today while napping during a football game, the light went out on the TV. So I see nothing. I guess somebody somewhere saw me ignoring the HD screen and decided I did not appreciate it!

[Tom Goodrick]

Today I learned that the problem was not in my TV but in the HD cable box. I need to get used to this complex system and try to understand it better. It turned out my wife solved the problem by simply calling the cable company and having them do things remotely to the cable box. We have our TV functioning at no cost.

[Tom Goodrick]

CAT UPDATE

As some of you know, we feed stray cats and they return the favor on occasion by bringing us their babies. It started when My wife saw that one cat was pregnant and gave it special attention with food on the back deck. A few weeks later we rescued three kittens from the dogs next door. They grew up in our house into fine cats but were too traumatized to give away to other people. They are my boys now - Alex, Buddy and Charley - big 20 lb cats.

Next the same mother (we didn't catch her that time) had five kittens and brought them into our garage. We raised them and managed to give them to a vet for adoption. We had the mother spayed. That was a year ago. She continues to live near our house, spending inclement nights in our garage. She is solid black.

Next another solid black momma cat showed up pregnant and got the special treatment. She brought five kittens to our garage in June. When hot weather came, mother and kittens were not doing well so we brought them into our 78F house. At 8 weeks we started trying to give away those kittens. We gave one - the only non-black one - to a friend. We still have the other four little black rascals. They occupy our mud room and laundry room whith daily excursions into our kitchen and sometimes beyond. They just turned 19 months.

These guys are all black with no distinguishing markings. We bought them all different-colored collars so we could tell them apart. They are now Danny, Elloise, Freddie and George. George can jump over our tallest barracade (48 inches) to run around the rest of the house. He hase met and made friends with our two dogs but not our big cats - yet. He's a real character.

It seems the bad economy plus a surge in the kitten population has created a large surplus of cats and kittens available for adoption in the north Alabama area. We have had no luck finding places to put them up for adoption. To make them more appealing now that they are not real small, we had them all "fixed" and gave them shots this week. Today we had been invited to show them with a local cat adoption club in front of a store in a strip mall. We prepared to do that, fixing up an old dog crate to hold the cats with a litter box while we stood around for a few hours. It rained. Now I learn that nobody recommends putting out black cats for adoption during the month of October because there are so many nutty people who like to use black cats for sacrifices in Satanic services. So we are standing down for the month of October.

Anybody want a free kitten by Fed Ex?

A stray yellow cat is about to have babies on/under our back deck.

[Tom Goodrick]

I wasn't going to write about cats, but, on seeing the last sentance in the piece above, I had to say something. Just yesterday we finished giving away the yellow cat and her four kittens. We had some help from a neighbor across the street who helped finance the operation and a farmer's wife who likes cats and has dealt with the problem of giving away kittens from wild cats. Mrs Yellow Cat had her kittens about 6 weeks ago in a shed a block away. She continued to come to our house for food and my wife had noticed she made frequent trips to that shed. Then two weeks ago when my wife took our Shetie out for his dawn patrol, there was a sudden and very loud "Meoww" from a patch of weeds in our "center garden" in the front lawn. The dog jumped back and barked. My woife pulled the dog back away and Mrs Yellow Cat came and picked up her son by the scruff of his neck and carried him into the garge.

Since we still have those five black cats, the kittens now five months old and as big as their mother, we did not not need more cats. That made a total of 13 which is very unlucky. So we turned to our local Government for help. We called Madison Animal Control which is operated from within our police department. Unfortunately, it was a holiday (Veterans' Day) so the animal control people were not on duty. They sent out a patrolman to assess the situation. I met him at the front door and told him my wife was in the process of trying to find and catch the kittens and their mother. He was a big and capable guy who could take care of the most recalcatrant humar brawlers. But he trembled at the thought of trying to get four fluff balls and their mother. He asked us to hold them a day. We agreed.

So the next day I tried many times to call the animal control people. I left several messages on their voice mail. In discussing the matter with our neighbor, she mentioned that many people become more interested when money is offered. She was aware we had just spent about $500 on our black kittens and their momma getting everyone protected with shots and spayed or neutered. meanwhile they had grown from being cute little kittens to being neat and beautiful cats. (People want kittens.)

After two weeks in which I re-constructed 4x4x2.5 ft kitten recreation quarters, emptied an extra litter box many times and my wife fed the babies their Gerber baby food, etc. Yesterday we rounded up the mother and gave a farmer's wife the four kittens in a box. My wife is nursing numerous scratch wounds from Mrs Yellow Cat when she tried to get the cat out from behind my tool cabinet. She has limited use of her left hand which was bitten several times. She was luck not to lose her left eye. i got the cat finally using a bass-fishing net which I held under the cat as she tried to climb a wall. That worked well and not even the cat was hurt.

So the problem of Mrs Yellow Cat has been solved.

[Tom Goodrick]

I'd like to put out some ideas about FS Rallies. It seems as though a good goal for a rally seems to elude us. In past years I have worked with Bill on the GAAR and I just finished the flights for the DC-3 World Rally for 2009. I have also hosted some orchestrated flying we called "flings" which began with a "Spring Fling" where we flew from the cold North to the warm South in the US. We have also done several Autumn Flings where we flew around Europe in autumn, starting in the north and following the frost through the mountains to the Mediterrainian.

The problem seems to be that the best goal we have come up with merely rewards conformity to mediocrity. We determine an average of some sort and then note the deviations from that average.

There has to be a better way but it has eluded me.

Here are some conceivable goals:

1. Teach some aspects of airmanship.

2. Show some intersting scenery.

3. Experience new aircraft.

4. Carry particular payloads. ( Investigate CG limits).

5. Show how to get there from here.

Everyone thinks he or she can fly a plane as well as most people and we want to show off. a race would be nice but it is hard to do a race for several reasons: we all fly different airplanes even when we fly "the same airplane" like a DC-3. We carry different loads. We choose to navigate in different ways. If we are forced to cut out some of those variations, it takes some of the fun out for many of us.

Any rally should promote the learning of good flying habits and the understanding of why we should fly that way.

Another problem with a race is that it fosters bad flying habits. I remember one guy who was convinced the fastest way to fly a plane was as low as possible since that is where the engine develops the best power. In FS that even seems to work in some cases though in real life the engine would burn out before you could finish such a race if it had any distance.

You can force people to fly at a safe altitude if you put some mountains in the way. This can work but you have to consider the aspects of altitude. If using unpressurized aircraft, the ceiling should be 12,000 ft. The rate of descent should be limited to 500 fpm. Though some young and very healthy peopl have different susceptibilities, one nmust consider the average person who happens to become a passenger.

Navigation is a big problem as I see it. I was a real-world pilot back in the 19070's and am very familiar with the limitaions of VORs and NDB's. Today the GPS navigation computers such as we have in the "Garmin 500" take away all of the problems of those antiquated devices - the need to zig-zag between VOR's and the position inaccuracies with ADF. I would add the real-world difficulties of being ablke to receive VOR's near mountains except that FS does not have that problem. The mountains do not block VOR signals in FS.

So I enjoy flying all over the world in FS using the GPS. I even use the GPS map to keep out of trouble when flying near mountains in bad visibility. You can find a river, large lake or offshore are in which to descend without hitting rocks. You can fly a long distance along a great circle merely by hooking your autopilot to a GPS flight plan. I have used this when flying around world several times, on both equatorial and polar routes.

The problem is that now, navigation is not a challenge. Anyone can do it. Of course we should have a rally now and then that makes sure everybody really can do GPS navigation.

Does anyone have other ideas for goals in rallies?

[Allan_Lowson]

As I am sliding gracefully back into the pack of mediocrity in the DC3 World Rally, I thought it was time to get my head out of the cockpit for a breather. Actually I am only getting my head into the cockpit at brief intervals between grossly overdue total repainting of the crumbling ancestral pile. My master-plan, of spraying the entire abode from floor to ceiling in the same shade of mucky mocha, tripped up when I discovered that different lighting levels have a dramatic effect on the apparent colour of the relevant wall or ceiling.

Which eventually got me round to thinking about Tom's suggestion (bet you wondered where this havering was heading) of tackling a different angle on the issue of rallies.

The GAAR, providing you are not allergic to the colour red or frozen beer, is an opportunity to try out something you don't fly often and see how well you can match a target flight time over a number of flights. While this caters for all levels of performance, from the full bore accuracy tyros to the flat out blinders, there is one fundamental catch - and if you haven't figured it out for yourself I'm not telling. I have wondered if there might not be a way of manipulating the system to optimise performance, but again you're on your own in figuring that out - just in case it might work.

Then the DCA World Rally, concentrating on the DC-3 or even the odd Lisunov Li-2, is a navigational exercise with the idiosyncratic scoring system of seeing how well you measure up to the average time and fuel consumption of every other nut flying the same route. I thought this was a brilliant system for the first three legs, but am becoming more uncertain as the legs and my relative fuel consumption pile up!

As Tom says, the apparent limit of flying the DC-3 actually allows a number of permutations of model and FDs. Modesty has led him to not mention that the hot tweak-de-jour is a set of FDs developed not a country mile from Atlanta.

The randomization that comes from using a moving average target eliminates much of the competitiveness and allows the competitors to concentrate on flying the navaids while trying to keep an honest eye on the throttle and mixture settings.

An exercise that throws in a variety of challenges such as the use of the GPS or varying CGs, or even single engine handling of a twin would give a different angle and may take us out of the comfort zones of the familiar.

One factor, which would probably be most successful in the States with the free access to on-line info, could be a repeat of the buy your own fuel challenge that was run a while back. In this you had to get from A to B and buy the fuel required along the way at current airport prices. This meant that the most direct route was not necessarily the cheapest, and you also needed to have the range to get between your preferred stops, or do a splash and dash at an intervening stop.

The issue of nefarious characters adjusting the performance of their aircraft cannot be eliminated by insisting on particular downloads being used. The honest will leave them alone, and if the only prize is virtual bragging rights then the temptation is less likely to appeal to the lower life forms.

However standard downloads with built in handling quirks might be an interesting idea. I remember many moons ago a flight sim programme that included the X-3 with positive feedback instability. The idea was to see how long you could stay airborne before turning into a large hole in the ground.

It would need someone with Tom's skills to generate them of course. Having said that there do seem to be many badly handling models to download, the idea here is for the handling issues to be deliberate rather than by happenstance.

[Allen Peterson]

Ive been thinking about this, need to do some more.
A couple of things ( I like Tom's 1.,2.,3., & 4.):
1. Would it work to have a test flight to determine the flight times, with the distance and route like the GAAR, and combine that with the fuel usage like DCA WR to determine the score? Each pilot would have a unique flight time, which he would report along with his fuel usage. Someone would have to do the flight time calculation...
With distance, time and fuel usage a cost per mile could be calculated. I'm not sure of the payload should or could be included (I'm not sure how it could be specified over various planes).
2. I like the GAAR approach to the eligible planes - 30s to 50s, no turboprops or jets. Or maybe twins, no turboprops or jets, and under 12000 gross, no fighters. Or maybe just turboprops (twins) or just light jets (no military).
3. How could all of this be organized, seems like a lot of work for someone.
4. I don't know of any way but the honor system to report results and plane performance.

My mind boggles...

Allen

[Tom Goodrick]

I've had a few days of significant illness to reflect on this stuff. It is good i finished the WR2009 because I am not sure when I can fly again with reasonable competance (if, indeed, I had much competance during Flight 10).

There is no doubt that one objective of a rally is for people to have fun and learn something at least a little bit new. WR2009 did this for me and satisfied the first 3 criteria for me. Regarding airmanship. I learned about flying in very high and very hot conditions. That was unique in my experience. I also confronted for the first time in FS conditions unsuitable for landing: ceiling and visibility too low and gusty wind conditions too high in combination with the poor visibilty. Upon recognizing those conditions I was forced to conclude that landing at an alternate airport was the best choice.

The third thing was to become familiar with a "new" aircraft. Of course I ahd flown a DC-3 in FS before - numerous short flights totaling maybe 25 hours. But this was the first time I flew nothiing but the DC-3 for over 17 flight hours. That was good. I became comfortable flying this wonderful old bird that I saw so often as a child. I will continue to fly it every once in a while.

But one aspect of the scoring problem still exists. You cannot look at the scores and tell "how you are doing". In some cases I am close to the average and in other cases I am well off the average. What sort of deviation is "good" and what sort is "bad"? Are we really trying to be as close to average as possible? Why would being average be good? In most things in life that is not true.

The GAAR scoring merely changes this to being close to your own average as opposed to being close to an overall average of all participants. In most GAAR versions, the "better" scores get within hundredths of a percent. Does that make you feel "proud" of doing a good job?