Power On Stalls, what's the point?

[Final 3 Greens]

Sensible

Indeed, Chuck's input, as always, would be valued.

[Charley]

So many techniques, so little time

I've been instructed on several subtely different stall recovery techniques during my travels, spanning powered aircraft and gliders.

Ultimately the recovery technique to be used depends, I suspect, on the nature of the stall and the point at which it is recovered (incipient or fully developed). Would I be right in saying that a stall recovery is, in the purest terms, to ensure that the angle of attack is reduced to within the critical angle and that laminar flow is restored over the wing?

In which case, if recovering from a power-on stall, wouldn't pitching to the horizon be sufficient, provided the angle of attack had been reduced? My logic being that the chemical energy of the fuel is then being converted into the kinetic energy (airspeed) required to promote laminar flow. This holds true if in a power-off (or unpowered) stall, as then you would be relying more on gravity to provide the airspeed required to restore the airflow.

Curiously, when I was converting onto gliders (which happened after I learned on power), I pitched forward during stall training with the CFI.

"What are you doing?" he asked.

"Breaking the stall," I said to Sir in the back. He then explained that I had been a little more heavy than I'd needed to be in the process. I was subsequently taught to progressively, smoothly and more slowly move the stick forward, until the wing was flying again. The reason being that this minimised height loss - always the aim when soaring.

It occurred to me that gliders pitch down by just enough to acheive the aim, because they have no other way of turning potential energy into kinetic (hence airspeed). So, with a powered aircraft, providing that the AoA was sufficiently reduced, wouldn't a pitch to the horizon be sufficient? Certainly that's what I was most recently instructed to do as part of my pre-commercial 'polishing'.

It'd be good to get some feedback from those with more experience under their belts...

[BEagle]

The exaggerated pitch attitudes taught by some for stall recovery are perhaps germane to this discussion.

We teach:

STANDARD STALL RECOVERY

1. FULL POWER AND CONTROL COLUMN CENTRALLY FORWARD...

(But not until the windscreen is full of ground, ONLY until an attitude is reached at which whatever it was that told you you had stalled no longer does so! That is probably only very slightly below the horizon; the shove-then-add-a-bit-of-power taught by some is TOTALLY INCORRECT!!)

2. LEVEL WINGS

3. RECOVER FROM ANY DESCENT

4. AND AT ALL TIMES MAINTAIN BALANCED FLIGHT!!

This works for any stall, the only difference with stalling in configurations other than clean is that flap should be deselected as for any normal go-around - once initial recovery has been completed.

[Final 3 Greens]

BEagle

Using your techique, what approximate height loss would you expect in a PA28-140 (say at 1900lbs), from a power off stall with land flap?

I am curious to compare your view with my handling notes/instructions from my PPL training in the last century, to see if I've been using the "shove and add a bit of power" technique!

If so, I shall repent immediately.

Reading the US AOPA accident report again they quote the PA28-181 POH as having a maximum hehgt loss during stalls of 350 ft - this sounds quite a lot to me

[smith]

When I posted this question never did I imagine it would stimulate a 6 page debate. Debate is good for the soul.

I have read with much interest all of the replies submitted and would like to thank all posters who provided both advice AND criticism of my flying skills. I have learned a lot from this post and am determined to iron out this flaw that has been exposed in my flying technique with an instructor before I fly solo again.

Thanks again all posters for taking the time to enter this debate.

Regards

Smith

Beagle

Maybe the clean departure stall is more applicable in the USA, I don\'t think there are any airfields in the UK above 7,000msl (or Florida, 17ft is highest point amsl in FL) which could attain an OAT of 25-30oC.

Sorry it was just an added comment I noted after reading all the posts again but I do appreciate what you are saying.

[Chuck Ellsworth]

O.K. Troops here are my comments.

First lets get this out of the way.

Quote:

.........................................

" it would be good to understand the FAA and CAA views and evaluate the differences in logic. "

..................................................

Before we can intelligently reply to the issues that Smith outlined in the first post here we must understand that connecting FAA / CAA and logic can be probmematic if we try and connect the dots using that avenue to search for an answer.

I see nothing wrong with the instructor expecting Smith to demonstrate correct control inputs into the recovery from the situation that the airplane had progerssed to.

He stated clearly that he was over controlling with rudder in a critical attitude at full power.

Further training in the handling of the airplane in question was not an unreasonable expectation on the part of the instructor that was evaluating his skills level to safely fly the Cessna 152.

I do not really think that something as acedemic as this issue required six pages of hand wringing and navel gazing to give him an answer to his question.

There that is about as simple as I can put it troops.

Your friend .....

Chuck E.

[LowNSlow]

Not wishing to appear dim but what is a 'whip stall' ?

[Final 3 Greens]

Chuck

Thanks for your thoughts.

we must understand that connecting FAA / CAA and logic can be probmematic if we try and connect the dots using that avenue to search for an answer.

I can see where you are coming from.

Maybe the difference of opinion between the two instructors at the FTO that smith reported was a result of trying to connect these dots and it then makes me wonder about the wisdom of mixing FAA and CAA training regimes (since there seem to be some differences in approach, but both systems produce good outcomes - a bit like different airlines SOPs), but that's probably way too far off subject

LNS

I believe that "whip" stall is another name for a stall turn, but no doubt someone will correct me if I'm wrong.

[BEagle]

It appears to consist of an aggressive pitch to the vertical, followed by a short tailslide and 'hammerhead'. Anyone who has been taught aerobatics will probably have experienced such an unpleasant manoeuvre during 'recoveries from the vertical'.....

After Docklands Doris' exit from the Royal Marines this very day in 1987, in the spirit of the 'Prince of Wales' left, right, pushover fleur-de-Lys vertical manoeuve, this vertical manoeuvre was nicknamed the 'Prince Edward' - pull up into the vertical, then give up!

[7gcbc]

have not read the full thread, but I have to say this.

power on stalls are very useful if you get the chance to experience them, often with surprising results that most of us would not realise happened until we performed them.

I did power on stalls in my PPL, and I now know why they are taught.

you **will** find them useful .........honest, especially if you do aeros, and what the hell, it does give you a better feel for the aircraft.

cheers

7gcbc

[TheKentishFledgling]

Not wishing to appear dim but what is a 'whip stall' ?

Simply another name for a stall turn / hammerhead.

tKF

[Genghis the Engineer]

Normally where the aircraft is stalled, then forced hard nose-down with the pitch control simultaneously with the pitch break, giving a very high nose-down pitch rate which can potentially damage the aircraft.

G

[Final 3 Greens]

power on stalls are very useful if you get the chance to experience them, often with surprising results that most of us would not realise happened until we performed them.

Yep, I'd buy into that.

[G-KEST]

BEagle seems to have it right in my opinion though the use of the term "hammerhead" might confuse those from across the ocean where it describes what we in the UK know as a stall turn.
My own definition of a "whip stall" is one where the aircraft is placed in an extreme climbing attitude, say over 70 degrees nose up, and at the stall the aircraft very smartly swops ends in pitch into a vertical dive. If the climb attitude is just below 90 degrees then any tailslide will pitch canopy up and if just over 90 degrees then any tailslide will pitch canopy down. Such a manouever certainly falls into the aerobatic category and if carelessly executed in terms of a very firm grip on all controls can certainly result in structural damage.
Cheers,
Trapper 69

[BEagle]

Yes indeed, Barry. Something we taught our RAF university air squadron students during early aeros lessons. But you couldn't do very many of these 'recoveries from the vertical' in one lesson before it would all go quiet as young Bloggs turned a delicate shade of pale green!

NOT a manouevre I would wish to practise in a traditional spamcan!

[MayorQuimby]

Hi Beagle,

You said:

ONLY until an attitude is reached at which whatever it was that told you you had stalled no longer does so

This is what I used to do instinctively until the CFI who was checking me out for my Flight Test told me to pitch forward until the speed had increased significantly over the stall (say to Vx) before recovering from the descent.

In trying to figure out why his approach was better I guessed that just making the stall warning go away might result in wallowing along on the back of the drag curve.

Do you think I was right after all?

[BEagle]

Not having been there, it's difficult to say. But if it's as you describe and the brief was to recognise and recover from the stall with minimum height loss, then yes, the CFI's exaggerated descent was wrong. Accelerating in a descent to Vx seems a self-defeating thing to do!

[Say again s l o w l y]

Wow, go away for a week and come back to ten pages of arguing around the point.

I still don't think that there is any real CAA Vs. FAA argument to have here. At the end of the day, you have to prove your competance to the person checking you out, it doesn't matter whether they're American or Martian.

My personal opinion is that everybody should experience spinning at some point in their training. An out of balance full power stall, should see to that nicely!

Stall recovery....... Keep the Bl**dy ball in the middle please!

[DFC]

Is there not a requirement under JAR to teach stall in the take-off configuration which, the last time I did it in a trainer was with no flap and the power at full throttle. I suppose it depends on how one describes take-off configuration but I will wait for the next Cessna to take off with the power at idle or even 1700rpm on a calm day.

As for the stall turn- a vertical climb to the maximum vertical extent at whic point the aircraft is rotated about the normal axis using rudder to enter a vertical descent and

whip stall - a stall entered from a deceleration that is well above the normal 1kt per second deceleration resulting in a positive often abrupt lowering of the nose at the point of stall.

Where we come from the standard stall recovery is always into the climb.

To judge how soon the pull out of the descent during the recovery the answer is as follows;

1. Aircraft reaches climb attitude but speed is above climb speed - pull out to late/ at too high a speed.

2. Aircraft reaches climb attitude but speed is still below climb speed - pull out too soon / at too low a speed

3. Aircraft reaches climb attitude at the moment speed reaches climb speed - correct.

Regards,

DFC

[7gcbc]

Hammerheads

Hammerheads are fun and relatively straightforward (timing) , but occasionally have the ability to scare the be-jazus out of you. The mechanics (physics) are fascinating.

and the buffet depending on the a/c is often a very clear and obvious cue to step on the rudder and use as much neutral pitch opposite stick (left hammer, right stick - counter the downgoing wing loss of lift (outside wing faster = more lift), right rudder, power off as she passes the horizon, approaches the near vertical downline)

if you get it wrong (and I have) you'll end up on your back due to both the torque (pronounced effect at low speeds) and the difference in lift on the down going wing and "top" wing (i.e the one on the outside) will put you embarassingly on your back DOOH!

its fun tho!

there is also a possibility of her sending you a very clear message by literally spitting you into a spin, usually in the direction of your hammerhead if you don't cut the power - now that wakes you up!!

The pitts is a case in point, very skittish so you need to be spot on with the rudder and stick - often going from a left hand spin into a right hand sans petit temps if you go to hard on the opposite rudder