With all the discussion of the floating issue and flaps, I started thinking about how the sim handles flap deployment in single engine planes.

I think in a high wing plane, the nose should lift. How pronounced should this be? I tried the 152 after modifying the flaps setting and the nose did lift.  Does this happen with the 172? This is what happens in XP, but it seems extreme in XP...very pronounced.

What should happen in a low wing plane? I tried the Bonanza and the Mooney. The attitude of the plane seemed to stay the same, but I did notice a loss of altitude. I feel there should be some change in the attitude when flaps are deployed, but I didn't seem to notice any. There must be some feeling or change. This doesn't seem to be simulated.

What should happen IRL?

It depends on the geometry of the flaps and of the aircraft.  In real life flaps deploying can influence how much propwash is going over the tail which also influences the pitch moment due to flap deployment.  I'm not sure if the sim models this with the Modern flight model or not. 

I have not flown a Bonanza in real lift but it seems like the flaps don't change stick forces a ton, based on Page 2 of this PDF - http://www.skyroadprojects.com/pdf/fbb pages.pdf

Quote

In this section we discuss some experiments conducted in an A36 involving changes in gear, flap, and power settings. We begin with the flaps. We reduce power to idle, extend the landing gear, and trim for 78 KIAS with the flaps up. The flaps are then extended, while we use one hand on the yoke and no trim change to maintain airspeed at 78KIAS. CAR 3.13101, under which the Bonanza was certificated, requires that this be possible without “the exertion of more control force than can be readily applied with one hand for a short period.” The A36 passes with flying colors—the stick force is zero. The sink rate, incidentally, stabilized at 800 feet per minute. Had we made an effort to reduce airspeed in proportion to the declining stall speed, the required aft stick force would still be quite light. If we reverse the above exercise, starting with flaps out and then retract them, again we find only negligible stick forces required to hold airspeed.

 

18 minutes ago, mikegrr said:

With all the discussion of the floating issue and flaps, I started thinking about how the sim handles flap deployment in single engine planes.

I think in a high wing plane, the nose should lift. How pronounced should this be? I tried the 152 after modifying the flaps setting and the nose did lift.  Does this happen with the 172? This is what happens in XP, but it seems extreme in XP...very pronounced.

What should happen in a low wing plane? I tried the Bonanza and the Mooney. The attitude of the plane seemed to stay the same, but I did notice a loss of altitude. I feel there should be some change in the attitude when flaps are deployed, but I didn't seem to notice any. There must be some feeling or change. This doesn't seem to be simulated.

What should happen IRL?

IRL airplane react different on flaps deployment . It also worth to mention  there are different types of flaps: split, slotted, fowler and etc Each type of flap will produce different ration between lift and drag. Some produce more drag than another. Generally speaking when flaps are deployed center of pressure shifts. This change creates a pitching momentum. I have flown planes that pitch up (after flaps deployed) and planes that pitch down. I don't think it has anything to do with low or high wing but rather with airplane design 

on the PA28 - low wings with simple slotted flaps (not fowler flaps that would increase wing area/camber) you would notice a tendency to ascend when selecting flaps 10 (first notch), a nudge of forward yoke is enough to maintain altitude.

The pitch-up tendency in a 172 is definitely very pronounced, so I don't think XP exaggerates it.

I'm currently a few hours into my flight training on a 172, and the first time I deployed flaps, the pitch-up caught me off guard, even though my instructor had cautioned me about it. You learn to anticipate it and start putting forward pressure on the yoke and reaching for the trim wheel as soon as you put in another notch of flaps. 

As others have said, it depends on the type of flaps and their position, and it also depends on the type of tailplane and its position too.

In most basic aerodynamics books on GA flying, there'll typically be a drawing of a plane with flaps deployed which shows the back end of the wing tilting down because this is usually the most common type of flap on a GA aeroplane and the easiest to understand in terms of what it does, i.e. it increases the curvature of the wing which makes it create more lift and more drag, which is a good enough explanation for ab initio training. What those kind of books don't normally delve too deep into, is what difference that makes in ground effect and what it does to alter the airflow toward the tailplane which is normally forcing the tail down, or what the increased wing camber does to the centre of pressure of the wing for that matter.

But there are of course flaps which don't simply alter the wing's camber, there are ones which also extend the wing area and there are also split flaps, which if you follow the theory found in those basic ab-initio books, shouldn't appear to work at all. Beyond this, on some aeroplanes, you also have ailerons which can droop with the flap deployment as well. And just to make things even more complicated, the lift increase on the wings for most aeroplanes when flaps deploy, is only on the inboard part of the wing, since that's where the flaps usually are. All this of course is not even getting into if there are slats on the leading edge too.

So, simple flaps which tilt the camber make the centre of pressure shift toward the rear of the chord, and without anything else affecting things, this would normally make the wing tip forward a bit more than it normally would. And since the air going over the wing is also forced downwards, this can affect what air is hitting the bottom of the tailplane which is there to counter the tendency for a wing to tip up from its trailing edge by imparting a tail down force, so depending on the position of the tailplane, this displaced airflow from the flaps might make it either more, or less effective at doing that.

So a good comparison for that would be the PA28 with a standard tailplane and the PA28 with a T-tail (usually the turbo models), since aerodynamically the wing isn't any different, just the tail. The alteration of the airflow on the tail with flaps deployed would be apparent on these two different variants and theoretically, the new flight model and airflow simulation in MSFS should mean this will be reflected in the sim on these two different configurations.

Oh, and the reason split flaps work when they don't really seem to follow the normal idea of a flap increasing the aerodynamic lift a wing generates because of either increased camber or area, is because they force air downwards, and as Newton's Third Law of Motion has it - For every action, there is an equal and opposite reaction - the wing is also forced upwards, but mostly from its trailing edge whilst creating a ton of drag, which is why that type of flap is better for landing than for taking off and in some types is never used for take off.

Thus it's not really possible to say flaps will always do this or that, it really depends on the aeroplane, you just kind of have to be ready for it in each one although certainly in some simulated aeroplanes in FSX and P3D, the effect is not as it would be in the real thing. Hopefully it will be better in MSFS in a month or so when that new airflow stuff is in the sim; that's when it will become much more than a pretty view generator.

Edited February 25, 20215 yr by Chock

In a GA plane, low wing like PA28 or Cessna C150 C172.

Flaps are lift generators, so when you deployed them, your nose full pitch down to provide better visibility at a lower airspeed to help for approach and landing.

In real life, yes you will feel a slight pitch up initially, but you want to correct your pitch by trimming it to release pressure when getting your desired airspeed attitude.

When retracting, you would want to do it in stages so that to lessen the lost of lift.  You will feel the sinking feeling when retracting from the last 2 notches.  Air speed will then pickup and trim accordingly.

I've only ever flown PA28s in RL, but those have a very marked balloon tendency when you deploy the flaps. You quickly learn to counteract it by simultaneously pushing forward on the yoke as you pull up the flap handle.

They're all different though. I've also flown in a friend's Socata TB-9 which is also a low winger but has completely different flying characteristics. Unlike the wide tapered wing of a PA28 which can quite easily take off with no flap deployed at all, the TB-9 which has a much more slender wing will seemingly just run and run and never get airborne without one stage of flap.

Edited February 25, 20215 yr by Tom Wright

I forgot to mention that in light GA some airplanes have mechanical flaps control and some have motorized. For example most Pipers have bar between seats to deeply or retract flaps while for example Cessna 172 has electrical switch. Those airplanes that have motorized flap control usually time  flap deployment so it would not cause sudden effect on aircraft control. Among motorized flaps there are usually two kinds: those when you set flap to desired position/angle like in modern 172, and those where you hold flaps down constantly to get to desired position manually. Among other Mooney 20J, Bonanza V35 both have flaps that you have to hold constantly. For example IRL when I fly in Bonanza I start dropping flaps from almost at midfield downwind (considering normal traffic pattern short approach) because they deploy very slow and in order to get full flaps on short final flaps had to deployed earlier. In contrast in my 182F I used to own flaps deployed very fast and you can feel it especially those 40 degree flaps make airplane slow down like a hand break LOL

When I was a student pilot, my flight school at 52F North west regional discouraged us to land (almost always  172SP) with flaps and with power. We had a short runway 3500 feet and didn't want us to float too much. Also when landing with full flaps, it becomes difficult to do a go around... I remember the first time I did a go around with full flaps, the pressure I had to apply on the yoke to keep the attitude reasonable while I floored the throttle was shocking. I used both my arms and all the strength I had to push the yoke, to make sure the Cessna 172 SP did not nose up flip over.... Tsk tsk.  Never experienced this on the sim.  One of the biggest difference between sim flying and real flying the 172. If a simmer goes real flying and you want to demo to him/her that real world flying is quite different than from simming, ask them to land with full flaps and then ask them to go around right away.. They most likely would panic as they increase the throttle with full flaps... LOL 🙂

Edited February 25, 20215 yr by Manny

4 minutes ago, Manny said:

When I was a student pilot, my flight school at 52F North west regional discouraged us to land (almost always  172SP) with flaps and with power. We had a short runway 3500 feet and didn't want us to float too much. Also when landing with full flaps, it becomes difficult to do a go around... I remember the first time I did a go around with full flaps, the pressure I had to apply on the yoke to keep the attitude reasonable while I floored the throttle was shocking. I used both my arms and all the strength I had to push the yoke, to make sure the Cessna 172 SP did not flip over.... Tsk tsk. 

That is a strange policy. I can only think of one case when full flaps not recommended for students. and it's for for older 172 models N, M (and before). The problem with student pilots is that they have difficulties with 40 degrees flaps. Like you mentioned go arounds or rounds up required some skill set that many student lack initially. So for example If I teach on older model 172 we start using 40 degrees flaps as we get to practice short field landing. 160ho 172 won't climb much on go around with 40 degrees flaps. There is also pitching momentum that student must compensate. So go around with 40 degrees flaps calls with immediate full power, flaps 40 to 30 degrees and carb heat off. After that climb and clean up the rest. I teach 30 degrees  for normal landings. Newer, 172 model starting with P, R,S do not have 40 degrees flaps anymore. I know some pilots do miss them as they allow steeper approached and shorter landing, but I guess there were to many accidents and so Cessna stripped them.

I am talking less than 5 year old 172SP with 180 hp engines. We had to do few flaps landings, even full flaps landing and go around to experience the feel. On final, almost always we had to land dead stick unless your speed is slow and need power.  and at mid point of the runway you had not touched ground (if we pass the gas station to our right, we had to go around and not try to save the landing. Cause on the south side, there are trees we had to climb over. any delay or hesitation means, sure accidents.   We also have a very narrow runway (the wings on both sides extend beyond the runway.  The Mantra is if you can learn to land here, you can land anywhere... HA HA! 

 

My first Solo was done at McKinney airport and then after a week I had to do another 3 solo landings/T&G on my home airport before I could go fly Solo.

I got good at Slips, get the aircraft dirty and come down steep and then land. I was so comfortable doing this. 

Edited February 25, 20215 yr by Manny

3 hours ago, mikegrr said:

 

I think in a high wing plane, the nose should lift. How pronounced should this be? I tried the 152 after modifying the flaps setting and the nose did lift.

Whenever I deploy flaps on the 152, the nose lifts. I always need to push on the stick to counter this. And this is without modifying any setting in the config file (if that's what you mean); it's the way Asobo have coded the flight model "out of the box".

3 hours ago, marsman2020 said:

It depends on the geometry of the flaps and of the aircraft.  In real life flaps deploying can influence how much propwash is going over the tail which also influences the pitch moment due to flap deployment.  I'm not sure if the sim models this with the Modern flight model or not. 

I have not flown a Bonanza in real lift but it seems like the flaps don't change stick forces a ton, based on Page 2 of this PDF - http://www.skyroadprojects.com/pdf/fbb pages.pdf

 

Absolutely what this gentleman says.

With the addition that in the Robin DR-400 One can expect a little Nose Up and then - just as suddenly, the Nose will drop. 

Think of it as a transition of dynamics and keep an eagle eye on the KIAS.

I think that's not a bad MO for most SEP. Your focus should be on Air Speed - whether Departing or Arriving.

And, of course, it goes without saying; your aerodynamic effects from Flap Deployment will be Totally governed by your Air Speed.

1) Too slow; wild pitch up.

2) Too fast - no perceptible change until too slow.

3) Correct Speed for the APPR - Not too much deviation from Stabilised.

I know which one I try and nail out of those three.

Edited February 25, 20215 yr by Will Fly For Cheese

14 minutes ago, Manny said:

I am talking less than 5 year old 172SP with 180 hp engines. We had to do few flaps landings, even full flaps landing and go around to experience the feel. On final, almost always we had to land dead stick unless your speed is slow and need power.  and at mid point of the runway you had not touched ground (if we pass the gas station to our right, we had to go around and not try to save the landing. Cause on the south side, there are trees we had to climb over. any delay or hesitation means, sure accidents.   We also have a very narrow runway (the wings on both sides extend beyond the runway.  The Mantra is if you can learn to land here, you can land anywhere... HA HA! 

 

My first Solo was done at McKinney airport and then after a week I had to do another 3 solo landings/T&G on my home airport before I could go fly Solo.

I got good at Slips, get the aircraft dirty and come down steep and then land. I was so comfortable doing this. 

Yes  dragging full flapped 172 with power in shallow approach is discourage. But certainly fuel injected 180 hp where neither worry of 40 degrees flaps or carb heat which reduce power significantly . Frankly I do not first solo my student on 3000 ft runway initially. I have luxury of 4300 ft.   runway.LOL Later, however, they go and land on 3000 runway for short filed landing. We have plenty of those with hills, power lines and threes around. Unless it's in Palm Spring in midth of summer it's not a biggie here in SoCal even with 160hp