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Stalling in Landing Configuration...?

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Stalling in Landing Configuration...?

Old 14th Apr 2018, 12:29
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Stalling in Landing Configuration...?

During one Bi-annual check-ride, the instructor asked for a 'Stall in the Landing Configuration'. I explained that this was a Cessna 172 and that it hadn't ever done stalls in the landing configuration. However he asked for me to set up the airplane, which I did... 75 knots, two stages of flap, and about 700ft/m rate of descent. I said my previous instructors had done 'Stalls with Flaps', but had never mentioned Landing Configuration.


Anyway we tried, but as long as we held 75knots / -700ft/m, there was no way the C172 was ever going to stall. We even tried 60 degree banked turns, but still no stalls...... We then went on to do some other exercises.


.
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Old 14th Apr 2018, 12:34
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Try it in something which bites next time...
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Old 14th Apr 2018, 12:56
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Well the only thing you can take from that is that you never managed to get over the critical angle of attack.

There is a exercise to which you should have done which is recover from an incipient stall in the landing configuration which is set up as you say then pitch up gradually maintaining a shallow decent until the stall warner goes of and then recover from there. Its not mean to be a fully developed stall or have a constant airspeed. It meant to simulate you pitching up on approach without adding power because you are low and not noticing your airspeed is decreasing.

The other one is a turn with partial configuration and again recover with the stall warner.

Its not the best idea of intentionally trying to get a fully developed stall in a steep turn, you can quite easily manage to stall one wing and not the other and get thrown over the top in either direction into a fully developed spin in a mode which may never have been looked at in the certification flight tests and may not be recoverable using the POH technique.
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Old 14th Apr 2018, 15:01
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scifi,

Try a similar exercise, using full-flap and full-power.

As an aside, 75 kts is a very high speed to be using for approach. Vso is 53-55 kts (depending on the model year).

A 55 kt approach speed will give you an easier flare and shorter landing. I routinely use this speed, with 50 kts over the fence, in a C182.
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Old 14th Apr 2018, 15:14
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Stall in landing configuration or approach configuration is essentially the same thing.
Many different ways you can practice a stall and it’s recovery and you should try them all under guidance:

- Wings level, maintaining altitude.
Landing config and power to idle and try and maintain altitude till the aircraft stalls. Attempt minimum altitude loss in the recovery without a secondary stall.

- Wings level, descending.
Landing config, power idle and trim for approach speed. Then slowly raise the nose while still continuing the descent as if you are trying to extend the glide on final.

- Banking, maintaining altitude.
Landing config or approach config.
Power idle and you’re mimicking a turn in the circuit.

- Banking, descending.
Landing config, power idle.
Mimicking a descending turn in the pattern.

Now do all of the above with different flap settings from UP to FULL down.
Purpose of all these excercises is multiple. Develop muscle memory for the recovery. Steer away from the ‘mental’ picture that the aircraft can only stall in one attitude in one configuration.


Honestly you’ve been done a disservice in your pilot training if you haven’t been taught all of the above plus all the ‘power-on’ variations.
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Old 14th Apr 2018, 15:18
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Scifi, Think of a "configuration" as not including a specific speed or power setting. "Configuration" is flap setting (in degrees on a Cessna, not "stages"), landing gear is already down for you, the prop is probably already fine, and you're not worrying about cowl flaps. With the configuration set, you're approaching the stall as the flight manual says: Slow deceleration. If you are maintaining the speed (75 knots is way too fast), to approach stall, you'll have to cause a change in something else, like increasing G. This is a massive deviation from a landing configuration type of flying.

A 172 will stall delightfully with any flap setting, and within 45 degrees of wings level, if approached with steady flight and slow deceleration. Yes, huge variations in power setting may also be used, and it is good to be familiar with the differences in how this affects a stall, however, I suggest that you perfect this all at low or no power first, and with your good technique refined, then start to repeat with greater power settings.

Early in section 5 of the later 172 flight manual, you will find the stall speed per flap setting and angle of bank. 75KIAS does not appear for any approved combination of these variables, so one could assume that you cannot safely make the 172 stall with any flap setting and 60 degrees bank.

I am relaxed with the idea that in general, 172s, like many other GA types, are stalled in landing configuration, mere inches above the runway, during landings.
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Old 14th Apr 2018, 16:25
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Stalling in landing config is one of the most important things to practice, especially being able to anticipate it.
As India 42 comments you could be at a much slower speed and the ability to feel the approach of a stall in this state is vital, it can happen (from personal experience). Can't understand it not being part of your training.
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Old 14th Apr 2018, 17:49
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Not disagreeing with my learned colleagues, particularly my friend DAR, but...

Originally Posted by scifi View Post
During one Bi-annual check-ride, the instructor asked for a 'Stall in the Landing Configuration'. I explained that this was a Cessna 172 and that it hadn't ever done stalls in the landing configuration.
Every aeroplane is stalled in flight testing for certification, in every configuration that can be achieved.

Stalling in the landing configuration is certainly here in Britain, quite often flown in aeroplane checkouts.


However he asked for me to set up the airplane, which I did... 75 knots, two stages of flap, and about 700ft/m rate of descent. I said my previous instructors had done 'Stalls with Flaps', but had never mentioned Landing Configuration.
If it's configured as for landing, it's in the landing configuration. The English language is a marvellous thing.


Anyway we tried, but as long as we held 75knots / -700ft/m, there was no way the C172 was ever going to stall. We even tried 60 degree banked turns, but still no stalls...... We then went on to do some other exercises.
Here's the wording in FAR-23, which is the certification standard which was used to certify the C172 (by bold).

Sec. 23.201 Wings level stall.

(a) It must be possible to produce and to correct roll by unreversed
use of the rolling control and to produce and to correct yaw by
unreversed use of the directional control, up to the time the airplane
stalls.
(b) The wings level stall characteristics must be demonstrated in
flight as follows. Starting from a speed at least 10 knots above the
stall speed, the elevator control must be pulled back so that the rate
of speed reduction will not exceed one knot per second until a stall is
produced, as shown by either:
(1) An uncontrollable downward pitching motion of the airplane;
(2) A downward pitching motion of the airplane that results from the
activation of a stall avoidance device (for example, stick pusher); or
(3) The control reaching the stop.
(c) Normal use of elevator control for recovery is allowed after the
downward pitching motion of paragraphs (b)(1) or (b)(2) of this section
has unmistakably been produced, or after the control has been held
against the stop for not less than the longer of two seconds or the time
employed in the minimum steady slight speed determination of Sec.
23.49.
(d) During the entry into and the recovery from the maneuver, it
must be possible to prevent more than 15 degrees of roll or yaw by the
normal use of controls.
(e) Compliance with the requirements of this section must be shown
under the following conditions:
(1) Wing flaps. Retracted, fully extended, and each intermediate
normal operating position.

(2) Landing gear. Retracted and extended.
(3) Cowl flaps. Appropriate to configuration.
(4) Power:
(i) Power off; and
(ii) 75 percent of maximum continuous power. However, if the power-
to-weight ratio at 75 percent of maximum continuous power result in
extreme nose-up attitudes, the test may be carried out with the power
required for level flight in the landing configuration at maximum
landing weight and a speed of 1.4 V<INF>SO</INF>, except that the power
may not be less than 50 percent of maximum continuous power.
(5) Trim. The airplane trimmed at a speed as near 1.5 V<INF>S1</INF>
as practicable.
(6) Propeller. Full increase r.p.m. position for the power off
condition.
Full back stick, unable to pitch up more, that's a stall as defined in the regulations. Full flap, extended gear (if you have extendable gear), power at pretty much anything between idle and 75% or full power, that's there too.


I think that, just possibly, the instructor might have known more than you did chap.


Also, if you're nervous of stalling a C172 with full flap, I'd suggest never ever even contemplating flying a PA38 without a grown up sat next to you!

G

Last edited by Genghis the Engineer; 14th Apr 2018 at 17:59.
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Old 14th Apr 2018, 17:52
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Quite easy, if a C172 ever stalls in fully developed landing configuration and slowed down - it does have a rigging problem. It is one standard I do first when renting out a 172. If it is rigged correct it will go to parachuting, not stall.
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Old 14th Apr 2018, 18:09
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Hi Funfly, I've done stalls in all sorts of ways, Accelerated, Power On, Power Off, Banked, Flaps and Flapless, but had never used the terminology 'in the Landing Configuration'.
There was no way I could stall the C172, and remain on the simulated glide path, maintaining the Landing Configuration... We used up a good 3000ft of airspace, and even pulled some fancy spiral dives trying...
.
As for the speed being high, my Checklist says... Normal Approach 65-75 KIAS. which I take to mean 75 on approach, and 65 over the fence.
.
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Old 14th Apr 2018, 18:53
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Hi Genghis, thanks for the details from FAR-24 Sec 23-201... So they say it is stalled if we hold the stick back for at least 2 seconds... Well I suppose I did that, but nothing happened in the same way that a PA38 would have responded.
.
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Old 14th Apr 2018, 19:00
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There was no way I could stall the C172, and remain on the simulated glide path, maintaining the Landing Configuration
You could stall a 172 going down, going up, or staying level - the engine power you've chosen will be the determining factor. If the engine is at idle, you'll be going down. The stall will be evident by your loss of pitch control, either you can no longer raise the nose, or you cannot prevent it from lowering. The path of the plan is not a factor.

You cannot safely stall a 172 at 75KIAS (refer to stall speed table in FM), so you're going to have to slow down to get the plane to safely stall in any configuration. If high speed stalls are in your plan, the aircraft should be equipped with a G meter. (As an aside, I find it amusing/alarming that the G limits are pilot limitations, which aside from a coordinated banked turn, the pilot cannot determine).

Landing configuration in a 172 will be any configuration in which you can land (flaps up or flaps down). There really are no variables which take a 172 out of landing configuration. If you have too much power, or too much speed, it won't land, otherwise, you're in landing configuration if you allow it to slow (hopefully over a suitable landing surface).

The actual C of G position will affect the stall indication to the pilot, between controls full back, descending, or nose drops while controls held well back - either is a stall. Happily, a 172 is very docile, and no matter how you stall it, will be recoverable with no excitement with adequate altitude. Stalls conducted with angles of bank exceeding 60 degrees, or G loading exceeding the limitations are unsafe, but certainly are nothing near flight from which a landing could easily be made.

There are some types (Ercoupe, for example) which are pitch control limited, to provide a stall barrier to the pilot. You can hold the controls full back, and the nose will not drop (though the plane may be going down!). This makes those types poor primary trainers - pilots need to learn to stall and recover.
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Old 14th Apr 2018, 20:50
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Originally Posted by scifi View Post

.
As for the speed being high, my Checklist says... Normal Approach 65-75 KIAS. which I take to mean 75 on approach, and 65 over the fence.
.


I've a fair few hundred hours on the 172/182. For me it's a little steeper than the three degrees I often see, and 55 all the way down final. A few knots more if it's particularly gusty. 75 is just plain silly. 65 is still ten too much.
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Old 14th Apr 2018, 21:56
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Hi Flyingmac, what you need is an Extra 300, then you can practice Prop-Hanging correctly.
.
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Old 14th Apr 2018, 22:28
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then you can practice Prop-Hanging correctly
A number of types will prop hang, the 172, just a little. Prop hanging in any form is very risky. In the case of engine failure, a gliding landing will not be possible, unless, you're many hundreds of feet up.

In general, 172's could be happily flown on a power on full flap landing approach at 60KIAS, and a gliding approach at 65-70KIAS. More speed is generally not helpful.
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Old 14th Apr 2018, 22:44
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If you want to fly an approach at an absurd and totally pointless 75 kts then fill your boots. But please don’t cry about floating, using all tbe runway available or going through the far hedge. But I digress. The stall in landing configuration is achieved by reducing speed (at one knot per second) until the stall, not by holding your approach speed.

PM

ps. Where did you get your checklist? Wherever it was, don’t go back. The POH has all the information you really need. No more and no less.
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Old 14th Apr 2018, 22:59
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One of the killers in flying is the turn from base leg on to approach stall. So I think as an exercise set it up with 30 of flap, 1500rpm, flying straight and level just hold altitude and wait. Min altitude 4000 agl and an instructor.

Due to the spiralling airflow of the prop normally one wing will stall first. The objective to correct with less than 500ft of height loss, because if not, your dead on a real approach. The idea is to teach how to recover and keep the speed up in the circuit add 4 kt for the turns. The first time I did this in a 150 the instructor never told me what would happen and I lost 1500 ft but only 150ft on the next try. Spin entry to the right over corrected spin entry to the left, while winding up the flaps and closing the throttle.

So I think it is an important exercise and teaches even the 152/172 can bit.

Note in a 172 with passengers in the back, it may not be so much of a pussy cat, pushes the CG back and ups the weight, which affects stall speeds and pitch sensitivity.
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Old 14th Apr 2018, 23:46
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Originally Posted by scifi View Post
..... but had never used the terminology 'in the Landing Configuration'.
You need to get out more.

Originally Posted by scifi View Post
There was no way I could stall the C172, and remain on the simulated glide path, maintaining the Landing Configuration...
Landing configuration has nothing to do with speed nor glidepath. As others have said it's all about aircraft configuration, i.e. position of the gear, flaps settings, prop settings, etc.
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Old 14th Apr 2018, 23:53
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Originally Posted by Flyingmac View Post
I've a fair few hundred hours on the 172/182. For me it's a little steeper than the three degrees I often see, and 55 all the way down final. A few knots more if it's particularly gusty. 75 is just plain silly. 65 is still ten too much.
55 all the way down final is also plain silly. A really good way to piss off any aircraft following behind you.

For a C172 or C182 speed down final should be from initially around 75 slowing to 55 at the threshold.
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Old 15th Apr 2018, 00:34
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Originally Posted by scifi View Post

Anyway we tried, but as long as we held 75knots / -700ft/m, there was no way the C172 was ever going to stall. We even tried 60 degree banked turns, but still no stalls...... We then went on to do some other exercises.


.
This is silly. The maximum Gee load permitted with the flaps down is +3.0 Gee. At 60 deg of bank you are already at 2.0 so a hard pull to try to get a stall is likely to get close to the max load.

There is no reason to do this and the POH is clear that spins are prohibited with the flaps down. If you did get it to stall with 60 deg of bank and lots of power you are going to be in for an interesting ride.

In any case the whole point of the landing configuration stall is to show the student that the airplane will be in only a slightly nose up pitch attitude when it stalls, unlike the introductory stalls where the aircraft will be in quite a nose high attitude. Therefore it is a good demonstration of the importance of maintaining the correct pitch attitude to maintain airspeed on final.

I always teach this exercise as if when on final, finding yourself low you raise the nose to try to get to the end of the runway instead of adding power.
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