Stalls, and turning.

[ben87r]

Turbo, although im with you 100% that these things should and need to be discussed ive herd 30+ first hand accounts of the incident at yppf and i still don't know for sure what lessons are to be taken directly from it. I like the idea that we are talking about issues but i dont think we can contribute these to the accident.

 

Could someone explain the physics of this please.

X2How can you unload a wind and increase bank?

 

And 60 deg is X2 over VS1... But i dont like the idea of doing it power off low level when in my AC ATM that = 24" cruise!

 

 

[turboplanner]

ben, forum discussions are quite erratic and not a means to analyse and determine the cause of an accident. In this case it looks like ATSB will be investigating, so there will be an interim report in a few months and a final report down the track.

 

In the case of RA accidents we've only ever seen a couple of ATSB reports.

 

In the absence of these reports, discussion is the next best thing;the value is in the spinoff discussions, where there's no reason not to follow a thread in great detail if it is teaching us how to safeguard ourselves in the future against issues which may have played no part at all in the crash we were originally discussing. I agree that the one you are talking about has several twists involving people other than the pilot.

 

 

[ben87r]

Ok, I may have misunderstood, i had thought that you had implied that this was the cause. I couldn't agree more about the discussion, the more that we can learn from others mistakes the better!

 

 

[Ultralights]

the initiator to a spin is YAW. as long as your BALANCED, you can stall (exceed the critical AOA) and still recover as usual, just enough forward stick to reduce AOA below critical angle. regardless of amount of bank.

 

practice a stall straight and level, and note the stick position, even at 30 deg, and 45 deg AOB, the stick will always be in the same position when you stall. i wouldn't recommend practicing it yourself though, get some proper EMT training, learn how to recover from stalls at all Angles of bank, and how to not get into a spin. and what to do if you find yourself suddenly upside down with the nose low. but a spin needs YAW. so keep the ball centred.. and resist the urge to tighten up the turn with rudder. even at steep angles of bank... keep balanced! if the nose starts to drop, roll off the bank, dont use the rudder!

 

 

[facthunter]

There's some strange things being said here. ( Not refering to you U/L).

 

A couple of points. Climbing turns will degrade the aircrafts performance so limit bank or you won't keep climbing.

 

Forget turning on rudder It is a balance control. If you use rudder, you are relying on the keel surface of the fuselage for the effect. Hardly an efficient way to create lift.

 

Angling the lift from the wings (banking) is the way to turn, the same as you have to go around a turn on a bike by leaning over. The wing has to provide enough lift to support the plane's weight plus some extra to turn it. The more bank the more lift needed.The extra comes from a combination of angle of attack and speed increase to maintain a safe margin above stall. If you want to be picky you are getting a little bit extra from the thrust line being higher but you can ignore that for practical purposes.

 

The extra angle of attack is obtained by pulling the stick to a new position as your elevator dictates what your angle of attack is. It is your means of controlling it. Everyone is aware that back stick is required when entering a turn and you have to move the stick forward when you are rolling wings level exitting a turn to maintain a height accurately. You increase power entering and reduce it at the termination of the turn. This can cause trim changes so accurate attitude control is needed, and possibly a bit of rudder pressure too. Medium bank (above 45 degrees) figure 8's with good throttle and height control demonstrate a good ability to co-ordinate controls and throttle and achieve desired airspeed and accurate height maintenance.

 

Steep gliding turns should be practiced occasionally and be able to be performed accurately but are not a normal manoeuver. 25 degrees of bank climbing and 30-40 otherwise in light aircraft would be somewhere near what I would like to see, Airliners use 30 degrees max for normal manoeuvering.

 

Anytime you have control difficulties in a turn the first consideration is to reduce bank angle. IF you are stalled the ailerons may not be usefull or exacerbate the problem unless you increase speed or reduce the angle of attack by moving the stick forward. If your speed is ample and increasing, (certainly not reducing) roll wings level with aileron as you are entering a spiral, which can be a significant problem if you don't recover quickly.

 

 

[boingk]

Thankyou for spelling it out, facthunter. I thought most of us on here were already pilots, but I'm beginning to doubt that if a matter as simple as this causes so much debate!

 

But that's exactly the point... IF the unexpected and potentially catestrophic happens' date=' WHAT ARE YOU TO DO?[/quote']Not sure if this is serious or not. If not, I'd simply get good old chap Watson to look into it and find a solution, eh?

 

In case it is - serious that is - it depends on the nature of unexpected and catastrophic event. Say you lose engine power, follow procedure and try and land in a clear spot. Hope you weren't skylarking at 500ft. If you lose evelator effectiveness you can fly on trim and throttle quite well. If rudder balance with throttle and aileron. If aileron then try rudder and throttle, although this is potentially most serious of most control failures.

 

If you encounter bad weather then you should of planned ahead better - turn back or go to alternate. If you hit a large bird at speed and your wing breaks off then don't worry, you're completely f***ed and the G-forces will instantly incapacitate you. If not, you've got a front-row view of your very own spectacular death!

 

Wonderous salutations - boingk

[kaz3g]

What you say is true Gentreau however one GA training airfield in South Australia uses a left runway and a right runway operating on different radio frequencies so there is a risk of head-on collisions when two aircraft are on their base leg if they extend that leg.Alan.

So does Moorabbin in Victoria.

 

Kaz

 

 

[Bandit12]

Thankyou for spelling it out, facthunter. I thought most of us on here were already pilots, but I'm beginning to doubt that if a matter as simple as this causes so much debate!

 

Not sure if this is serious or not. If not, I'd simply get good old chap Watson to look into it and find a solution, eh?

 

In case it is - serious that is - it depends on the nature of unexpected and catastrophic event. Say you lose engine power, follow procedure and try and land in a clear spot. Hope you weren't skylarking at 500ft. If you lose evelator effectiveness you can fly on trim and throttle quite well. If rudder balance with throttle and aileron. If aileron then try rudder and throttle, although this is potentially most serious of most control failures.

 

If you encounter bad weather then you should of planned ahead better - turn back or go to alternate. If you hit a large bird at speed and your wing breaks off then don't worry, you're completely f***ed and the G-forces will instantly incapacitate you. If not, you've got a front-row view of your very own spectacular death!

 

Wonderous salutations - boingk

Boingk, I get a sense from your rather evident sarcasm and somewhat morbid scenario that you are unwilling to allow for any grey, preferring a black or white approach. That's all well and good in theory, but doesn't happen to fit well with reality. So we have established that you will never allow yourself to get into a sticky situation, particularly when it comes to control failures or bad weather. Great work, but I'm afraid that I'm not at your level of competence, and I am sure that there are many others (not just me) who are happy to admit that they also have gone up (after getting a properly considered wx report), only to find that things are a bit more marginal than expected.

 

When it comes to stalling in a turn, it would be great if we could all avoid it as you plan to do. But flying isn't black and white. I've said it before, all that is needed is one distraction or preoccupation (I know, I know, you don't get them because you planned ahead better), or heaven forbid, encountering windshear turning final which may cause you to get uncomfortably close to a stall at less than 30 degrees AOB (I know, I know, you would have been aware of the wind conditions and carried an extra 20 knots to cover that).

 

Please excuse my sarcasm in return, but this is the Student Learning area and not everyone reading this has necessarily got a really good grasp of what is happening in a turn. All this thread has really highlighted is that there is a lot of confusion about flight at the lower end of the envelope, especially regarding stall speeds and turns and "unloading". I suspect that a number reading may not even quite get what unloading is, or why it affects stalling. Perhaps one of our more experienced members like Nev may like to start a new thread on unloading, or DJP from an aerobatics instructor perspective may be able to explain it better.

 

 

[djpacro]

... I suspect that a number reading may not even quite get what unloading is, or why it affects stalling. Perhaps one of our more experienced members ...... or DJP from an aerobatics instructor perspective may be able to explain it better.

Happy to discuss over a glass of red wine or in the hangar but online it is easier to point people to this magnificent free resource at http://apstraining.com/ - simply register for free and browse the material or download the free book on upset recovery training.

[boingk]

Bandit12 - no offence taken. I realise my reply is a bit out of the ordinary but there is a reason we have as many sophisticated resources available to us as we do in aviation; specifically for our safety and that of others. I'm not trying to upset people at all, but sometimes I just find it highly aggravating to see a discussion on a basic issue blown out of all proportion.

 

There is a reason I don't fly in 'marginal' weather. I've trained and done the majority of my flying in and around Goulburn NSW and the weather here can vary a lot in only an hour, or even just a few miles away. I don't like flying in or around marginal weather - I've done it plenty of times in rented aircraft from the flight school and refuse to do it in mine if I can help it... which I can.

 

I'm not trying to start a debate about conditions or failures, just encouraging proper procedure and preparation. Good, solid, sensible things.

 

Happy flying - boingk

 

 

[Powerin]

Thinking aloud....would a simple forward/back stick position indicator serve as a rudimentary AoA indicator? Perhaps something similar to a Jabiru flap position indicator and have a red line where the stall position is?

 

 

[facthunter]

NO because the actual position varies with Cof G, flap and power setting. For a given situation/configuration it is a valid concept. Some instructors reject the concept. I don't. Moving tailplane (horizontal stabiliser) trimmer situations don't obey this concept. You can trim them to stall and the stick stays where it is normally. You just change the range of it's authority. Nev

 

 

[Bandit12]

Nothing beats doing lots of stalls in lots of different configurations (and at least incipent spins), and training to recover instinctively.

 

 

[M61A1]

but this is the Student Learning area and not everyone reading this has necessarily got a really good grasp of what is happening in a turn. .

The reason this discussion was started was because we've seen more than a couple of stall/spin events in the circuit area in recent times, and not from inexperienced pilots. I don't know why these events occurred, but I doubt it's from a lack of understanding, distraction? maybe.

Tomo was just putting out a gentle reminder that complacency while turning (particularly low and slow) can and will kill you.

 

 

[turboplanner]

....well it has exposed a massive lack of understanding so that's a good thing.

 

The scary part is that lack of understanding is quoted by people who in most cases are supposed to have received training, guidance and assessment by qualified Instructors.

 

 

[Ultralights]

NO because the actual position varies with Cof G, flap and power setting. For a given situation/configuration it is a valid concept. Some instructors reject the concept. I don't. Moving tailplane (horizontal stabiliser) trimmer situations don't obey this concept. You can trim them to stall and the stick stays where it is normally. You just change the range of it's authority. Nev

if the elevator/stabilator can be trimmed at the stall position, then wouldnt the stick still be in aft position? possibly not at the exact position of the stall with flap up, but very close? there is a solid cable or rod connection, how could the yoke still be relativly normal yet the elevator/stabilator be in a position close to a stall?

 

when trimming the savannah to fly at 40 kts, the trim tab is a long way down, holding the elevator in a up position, and the stick position reflects that, though there is no force needed by me to hold it there.

 

 

[facthunter]

U/L because the elevator is not moving in relation to the horizontal stabiliser. The whole tailplane moves in response to the horizontal stabiliser moving. The elevator streamlines with it. You would have to apply out of trim forces to the elevator to change that, requiring displacement of the stick.

 

Other trim systems displace the elevator, and the stick follows the elevator movement and give the result you describe. Nev

 

 

[Bandit12]

Personally I worry about "stick position" as a measure of impending stall. I know that simple examples are needed when a student is brand new and trying to cope with far too much information, but dropping your eyes to the stick (or yoke) to try and work out where it is at would surely distract your attention from "out there" where it might be really needed.

 

 

[facthunter]

I would never recommend looking at any stick markings. The pilot should be "conscious" of (roughly) where the stick is. As an example landing a taildragger 3-point, you are really aware that the stick is way back. In a crosswind (extreme or limiting) landing you should know how much stick travel and rudder travel is left, Not by looking there (You should be looking other places) to be aware of what the plane is doing. If you are running out of control authority you should not procede with the landing, but you don't look at your control position. You need to be familiar enough with your plane not to need to. Nev

 

 

[Ultralights]

you shouldnt need any markings, you can feel where the stick is through your hands. if its a centre stick, in normal cruise, the stick might be level with your knees, when doing stalls, its might be right back in your crotch, so when you feel the stick is approaching your crotch area, where you remember it being during stalls, then its a good bet you will be near the stall.

 

 

[djpacro]

Seems to me that people are more likely to get into trouble in those aeroplanes which behave more aggressively than many trainers at the stall or which have nil or negative stick fixed static stability.

 

For example, a nice tapered wing with not quite enough washout or the leading edge profile not exact enough can have quite unacceptable stall characteristics. The RAAF had a problem after wings of their Macchi MB 326s were rebuilt.

 

Stick position movement is a function of stick fixed static longitudinal stability. If you fly a nice stable aeroplane then much of the above discussion applies - especially if you do an EMT course in an aeroplane with no flaps and you don't get to see the effects of cg changes.

 

Longitudinal stability requirements for certified aeroplanes typically mention stick free stability. Pilots feel stick forces which relate to stick free stability. What about uncertified Experimental home-builts?

 

The diagram below shows how elevator angle (treat it as stick position for this discussion - stick back is top of the diagram) varies with airspeed for trimmed, stable flight. Flaps 10 deg at aft cg the stick position remains the same for all airspeeds down to - oops, must be a nose-up pitch somewhere there to need to move the stick forward before it stalls, I guess. Where do you think the stall stick position might be?

 

 

More info on this aeroplane at http://www.eaa1000.av.org/fltrpts/lanc360/hq.htm

 

 

[facthunter]

You are talking of a design with unstable pitch reaction. In many quarters such a response would prevent the plane being allowed to fly. ( as I have been led to believe). Nev

 

 

[djpacro]

They were flying around for a while like that, perhaps still. Nothing preventing a home-built to be built and behave like that.

 

And some well-known older, certified GA aeroplanes have similar characteristics in some configurations.

 

Take a peek at page 28 of NASA TN D-3726, "An Evaluation of the Handling Qualities of Seven General-Aviation Aircraft" at http://www.nasa.gov/centers/dryden/pdf/87726main_H-451.pdf

 

You can see that the stick fixed stability is only neutral.

 

 

[facthunter]

I'm a great admirer of Bill Whitney's approach to all this. He is very practical. He put out a disc and notes some years ago, which I would recommend to all novice builders and some a bit further on than that for consideration. The aerodynamics are proven and structures analysed thoroughly without you having to have a degree in physics and maths. I don't know whether he still does them but there must be some still around. It stops people having to re-invent the wheel and make the mistakes that someone has already done for you. he made the Whitney Boomerang and did most of the work on the Southern Cross replica, design wise. plus other stuff.. Nev

 

 

[Ballpoint 246niner]

Wow, what an enormous and well versed treatise on the aerodynamics of the stall in this thread. All fantastic stuff and in depth has been published time and time again. I try to keep it so simple for my sake as much any one else,

 

Know the stall symptoms, know your aircraft intimately, and don't go near there - unless less than a foot of the ground on landing or lots of height for practice. End of story, finato, done!

 

Maybe I'm just too dumb and simple for all this flying stuff.....