lift increase whan applying flaps

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bobsk8
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Re: lift increase whan applying flaps

Post by bobsk8 »

I wrote this on another thread, and decided to post it here too. I solved my problem with poor landings with the C 172. I used FSUIPC for the elevator axis instead of the sim controlling it, and then I set the curve in the elevator axis to +4. Now no more endless floating and ballooning during the flare and all landings are silky smooth. I also returned the elevator effectiveness in the C 172 aircraft cfg to the default of 2.
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Oracle427
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Re: lift increase whan applying flaps

Post by Oracle427 »

Yesterday, I went up for a flight in a 182 from KCDW to KMQS to meet some friends along with my wife. I therefore couldn't use it to conduct any real tests lest I make her airsick. :)

I closely observed how much forward pressure I had to apply on the yoke when I added the first 10 degrees of flaps. I was going about 100 KIAS and had to push forward approximately 1 inch on the yoke to keep the airplane from climbing. As it slowed down to around 85 KIAS I was gradually able to relax most if not all of that forward pressure.

I would estimate that required at least 20 lbs of force at its peak as the 182 yoke is quite heavy. Additional flap didn't require much pitch input on the yoke.

Next time I'm alone, I'll try to test how much the aircraft will climb and the changes in airspeed without intervention.
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Nick - A2A
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Re: lift increase whan applying flaps

Post by Nick - A2A »

Interesting test result. :) Yeah, it would be good to hear what happens if you're able to try first stage of flap extension at around 100 KIAS without touching the yoke or throttle next time you fly without Mrs Oracle. :)

In the sim, the power setting seems crucial. I think if the flap extension coincides with a power reduction as you mention, the pitching moment will be significantly weakened.

Thanks,
Nick

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Oracle427
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Re: lift increase whan applying flaps

Post by Oracle427 »

In this flight, the power reductions came well before adding in flaps to slow down from 135 KIAS to 100KIAS before adding in flaps. The problem is I can't tell you the engine performance numbers in terms of the 182 sim, as this thing is running a lot of boost. Descent MAP is 45 in HG, yes forty five.
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AKar
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Re: lift increase whan applying flaps

Post by AKar »

Oracle427 wrote:The problem is I can't tell you the engine performance numbers in terms of the 182 sim, as this thing is running a lot of boost. Descent MAP is 45 in HG, yes forty five.
Diesel?

-Esa

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Oracle427
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Re: lift increase whan applying flaps

Post by Oracle427 »

Yes
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AKar
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Re: lift increase whan applying flaps

Post by AKar »

MAP indications on those (where available) can indeed be rather...curious if one's used to the regular gasoline engines. :) And of course, not comparable. In principle, if we took the turbo away, the MAP in diesel would show more or less the ambient all the time, regardless of the power setting.

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Oracle427
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Re: lift increase whan applying flaps

Post by Oracle427 »

Oh that's true, I hadn't thought about that! I certainly wouldn't want to find out how little power it would generate at ambient pressure. TO boost in these conditions is around 85 in.

45 in is carrying enough power to hold altitude and keep the CHTs conservatively warm to avoid a flameout in the pattern. This raises the question if my test is therefore flawed as I might be carrying more power than one would normally be carrying in an AVGAS unit at the same phase in the pattern when flaps are initially applied. It was still interesting to see that I needed that much movement of the yoke. I actually didn't expect it to require that much to maintain level flight.
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AKar
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Re: lift increase whan applying flaps

Post by AKar »

Oracle427 wrote:I certainly wouldn't want to find out how little power it would generate at ambient pressure. TO boost in these conditions is around 85 in.
Years back, my brother and I had a VW Golf estate with 1.9 SDI it think, which was naturally aspirated diesel. A hard push on the pedal primarily caused a change in noise, whereas the speed meter could be checked, for example, when the song in the radio finished if it was given enough time to rise. Performance: Nil. :mrgreen: It was relatively economical, though, and very reliable. It did very good in winters too for some reason, cold-starting without real issues well down to -30 °C, if one didn't get hasty on pre-heat. The next diesel I was driving more, a quite recent Audi A5, started by a button as well, but sounded like it was asking me to put her out of her misery when crunching through the first minute or so in that cold!

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Oracle427
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Re: lift increase whan applying flaps

Post by Oracle427 »

Not the case here. This diesel is rated fore the same power as the O-470U it replaced. If you push forward on the throttle you get a very nice push back into your seat. Keeping the engine cool is a very real concern as the oil temps spike up very rapidly in climbs in warm weather. That is the most limiting factor as you need to give up sustained climb performance to get sufficient airspeed for good cooling.

It does not like starting in the cold and vibrates like mad until oil temp starts getting close to 65C.

I'm not sure if ours is a bit flaky, but starting in temps below 5C starts to get a bit questionable with a cold engine. The glow plugs just don't seem to give enough heat to ensure ignition every time.
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AKar
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Re: lift increase whan applying flaps

Post by AKar »

Oracle427 wrote:It does not like starting in the cold and vibrates like mad until oil temp starts getting close to 65C.

I'm not sure if ours is a bit flaky, but starting in temps below 5C starts to get a bit questionable with a cold engine. The glow plugs just don't seem to give enough heat to ensure ignition every time.
With diesels, especially the relatively classic ones as seen in the work machines and such, the fuel is the key to cold operation. I don't know how JET-A for instance compares with winter-grade diesels (except for that its filtering properties remain good). It would make an interesting thing to study out for one evening. :)

And yeah, most diesels run very rough when started at extreme cold, even with appropriate fuels to the condition. This is rather normal, and to a great extent, unavoidable. The effect of the glow plugs' pre-heat mostly vanish after first several engine revolutions when the engine is turning. That's why it is imperative, when starting some old-school, completely manual/mechanical diesels that they are pre-heated painstakingly before starting attempt to not waste the battery power. Modern automotive ECU-controlled, direct-injected diesels do surprisingly good job with their starting automatics, IMO, almost never failing to start.

-Esa

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Re: lift increase whan applying flaps

Post by m_disco »

FLYING TIGER wrote:Ok Nick, I will check the link you provided. Hereby what I'm talking about. Flying strait and level, hands off and then applied 10° of flaps without any compensation with the yoke. I just leveled out a bit when the nose started to rise again and I tried to keep the VS more or less at 0 f/min. T keep it there there is quite a bit of trim foreward, otherwise the nose rises again but as much. I you would like to film this also please let me know.
....

https://youtu.be/0pWMT1-ydyA
I've been watching this topic with interest as my experience in the real plane led me to believe that this is how it would actually behave. One would not normally be flying along at 100kts, and apply 10º of flaps with 2000 rpm still on the engine. You're generally trying to slow down so would have much less power on the engine when initially deploying the flaps.

This weekend I was able to take a 172R out to the practice area, along with my camera gear, and test what actually happens in the same scenario as the linked video.

Conditions:
- 2006 172R with G1000 & 2 180lbs pilots in the front seats, 3/4 tanks.
- Altimeter ~3013, temp ~5ºC, ~ 3000 pressure altitude
- Engine at 2000 RPM and trimmed for level flight at 97 knots IAS
- Flaps deployed to 10º and no pressure applied to the elevator control axis of the yoke

Results:
As the flaps extended, the aircraft quickly started pitching up, climbing and bleeding off speed.
I intervened as the nose pitched through 12º nose up, and observed a peak indication of 15º nose up on the attitude indicator.
Airspeed had dropped to mid 70's and we climbed around 200' before I fully recovered.

Conclusion: This 'aggressive pitch up' moment in the a2a aircraft is correct.
If anything, based on my experience and in comparison with the video posted above, it could be a bit more aggressive. Although, that may be due to a difference in CG from my test and the settings FLYING TIGER has in his video.

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Killratio
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Re: lift increase whan applying flaps

Post by Killratio »

Glad you were able to test it so directly M_disco, thanks for the input!

Not at all strange that it is correct...given that quite a few of we beta testers have hundreds of hours on the R model... ;)

The difference between real response and FSX default aircraft response still baffles a lot of sim pilots. As does the difference between real control distance of travel and your average Saitek set up.

I always chuckle when people complain about the strong pitch up on takeoff as well...but that is exactly what the real aircraft does.

Anyhow, cheers for the real world comparison, glad you like the R

best regards

Darryl
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FLYING TIGER
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Re: lift increase whan applying flaps

Post by FLYING TIGER »

Hi guys,

to finish this topic for me, a last comment. First of all a big thanks to all of you who participated in this topic and the efforts you took to reply. I have no doubt that every effort is made to make the 182 as close as possible to the real thing. What wondered me the most is that, when I look at the Youtube vids, that for one reason or the other some people seem to experience different things when applying flaps. But hey, it is what it is. Because I actually don't care if my 182 acts 100% like the real thing or not, I just wondered if there was a way to adjust the flap behavior in one a way or not. That was intentionally the reason for posting my question. Now all I can do is try to make a smooth adjusting of the yoke and the trim when aplying flaps as possible, but I'm not realy happy with it. Can't get it right enough for my liking. Hope practice makes perfect in the end :-). But,...the 182 is still my basic and favorite GA airplane and I fly it 90% of the time.

Thanks again and keep the blue side up!

Eddy

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Nick - A2A
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Re: lift increase whan applying flaps

Post by Nick - A2A »

m_disco wrote:This weekend I was able to take a 172R out to the practice area, along with my camera gear, and test what actually happens in the same scenario as the linked video.
Excellent testing m_disco - thanks for doing that. Did you keep the footage by the way? Either way, I'm convinced. :) The only slight question mark remaining for me is why the KAP 140 is unable to handle the pitching moment, unlike in the 182T vid I posted earlier in the thread. I still suspect this is because the pitch response in the 182 with the first stage of flap is a bit more sudden than the flap transit speed (which is apparently significantly slower than in the 172) suggests.
FLYING TIGER wrote:Now all I can do is try to make a smooth adjusting of the yoke and the trim when aplying flaps as possible, but I'm not realy happy with it.
You could also try timing it so that you make a power reduction just before you add the first stage of flaps Eddy. This should help a bit as the tendency for the nose to drop when you reduce power should partially counter the pitching-up moment caused by the flaps.

Cheers,
Nick

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