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djpacro

Stalls

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You're correct aro.  I jumped in without thinking properly.  It is a maximum, not a minimum.  However, the idea of adopting a minimum manoeuvre speed is still focusing pilots on looking inside at a dial instead of knowing when the wings is close to stall, or knowing how to fly it at, or under stall speed.  You're right, I didn't watch the video, but did you read my whole post?

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1 hour ago, Manwell said:

did you read my whole post

I did.

 

Some people believe that with enough training we can all improve our skills enough to eliminate accidents. That approach regularly fails.

 

Yesterday we had Australia's most skilled footballers playing in the Grand Final. No-one doubts their skill, they do plenty of practice, but still their skills occasionally let them down and they miss easy kicks etc. No matter how skilled you are, the risk of a skill error is always there.

 

There are areas of aviation where they refuse to rely solely on skill to avoid accidents. They have rules and procedures to keep away from the areas where skill becomes critical. Those areas of aviation tend to be the safest areas by far.

 

I have no objection to stalling an aircraft, but I only want to do it when I have planned it. The idea of a defined minimum maneuvering speed, to stay away from the area where skill becomes important is interesting.

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16 hours ago, aro said:

Some people believe that with enough training we can all improve our skills enough to eliminate accidents. That approach regularly fails.

It does regularly fail aro, and there are good reasons why it does.  In simple terms, all accidents are subconsciously caused, or allowed to happen by the pilot.  Nothing external to the individual can change those factors, but QANTAS's example demonstrates that a culture can be constructed that can eliminate accidents.   

 

The most important factor is always missing in any of our previous attempts, and that is ensuring what we're doing is right.  We don't really get to decide what's right either, do we, since CASA dictate the syllabus and fill it with so much extraneous rubbish that instructors don't have the time or inclination to prove the validity of the things they teach.

 

As Mark Twain famously said, "It ain't what we don't know that gets us into trouble, it's what we know for sure that just ain't so."

 

You're right about commercial and military aviation relying more on rules and procedures to ensure safety, and they are safest, but it is at a great cost.    I've been in a multi-crew operation, and it wasn't healthy, despite it being safe.

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But People do still stall and without knowing your actual weight and  "G" you do NOT know your actual stall speed. Pilot's can't be constantly relating their bank angle to a speed increase either.  The position of the elevator is  the main determinant (all other things being equal). Stall is an AoA thing not a bank angle thing by itself.  Nev

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The advantage of training and doing stalls is that we can learn to recognise the onset of a stall. I know when I am slow on approach, with little feel in the stick, that if the wing starts to drop I need to use the rudder to pick it up. Funnily when I am even slower during the flare it is safer to use the aileron to level the plane off. All due to ground effect I think.

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Ground effect does help but don't count on it. Picking a wing up with rudder is a great theory but at that point you are in a touchy situation, especially when low and with some mis-rigged planes. I used to fly a pretty rough Auster (because it was cheap) which would always end up rolling to the right at the ultimate point of stall regardless of how wing low to the left you were holding it with aileron and/ or left some rudder. .. By various means ONE learns  if you are lucky enough to survive. Practice  and more knowledge, makes you more lucky. Nev

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On 30/09/2019 at 9:51 AM, facthunter said:

But People do still stall and without knowing your actual weight and  "G" you do NOT know your actual stall speed. Pilot's can't be constantly relating their bank angle to a speed increase either.  The position of the elevator is  the main determinant (all other things being equal). Stall is an AoA thing not a bank angle thing by itself.  Nev

Right, people still stall without knowing their weight, G, or stall speed Nev, but they don't need to know any of those.  Elevator position is one part of the puzzle that enables a pilot to "know" when they're about to stall, but it's not the only one.  The others include high pressure on the bum, followed by a loss of pressure, wind noise and control feel.  THE ONLY WAY for a pilot to become attuned to the various factors is through experiencing them, and it's not that hard, or risky to do so provided it's done methodically.

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I'm wondering how this can be done in a modern context. I was (lucky to) able to do dogfighting with other instructors in (almost) unbreakable planes and toilet roll cutting and balloon busting as well as aerobatics and teaching them.. Another age another era. It will never come back.

    . At the other end of the spectrum,  coffin corner where the altitude induced stall meets the MMo M crit  (buffetting) stall. people would be alarmed to know what small margins exist there in some of the planes they fly in.

   Also   Service ceiling and Absolute ceiling. where you pull the stick even a small amount and you descend.. How can this be done today?. Actually stalling airliners in training. That's never going to happen again. Fortunately good simulators have taken over some of it.  As they should.

  The system does have a problem. Lots of people got killed in training, especially with VMC (a)  which still kills people in perfectly good / serviceable aeroplanes. Many ways of losing control of a plane with generally serious consequences.. IF you aren't aware .Nev

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48 minutes ago, facthunter said:

I'm wondering how this can be done in a modern context. 

At the other end of the spectrum,  coffin corner where the altitude induced stall meets the MMo M crit  (buffetting) stall. people would be alarmed to know what small margins exist there in some of the planes they fly in.

Also   Service ceiling and Absolute ceiling. where you pull the stick even a small amount and you descend.. How can this be done today?. Actually stalling airliners in training. That's never going to happen again. Fortunately good simulators have taken over some of it.  

The system does have a problem. Lots of people got killed in training, especially with VMC (a)  which still kills people in perfectly good / serviceable aeroplanes. Many ways of losing control of a plane with generally serious consequences.. IF you aren't aware .Nev

Any problem has a simple solution Nev, and then experts and authorities jump on the bandwagon.

 

If there is a persistent problem in any system, the last place you'd look is where the cause is found.  Using a building analogy, if walls or ceiling start cracking, we know it's not the walls or ceiling that are the problem, and the same is true with every other persistent problem.  Where we're looking for answers isn't where the answers are, they're usually much deeper in the foundations that have been laid so long ago they're forgotten.

 

In this context, the whole problem stems from a poor appreciation of aircraft manoeuvrability in the transition to stall and below.  The first corrective action is to give pilots sufficient exposure to flight at stall speeds that they instinctively "know" when an aircraft is mushing, and how it responds to more back stick, more power, not enough rudder, or too much aileron.   This is initially done at altitude until proficiency is gained, then over the runway as low as possible without touching.  Eventually the aircraft does touch down even if it's intentionally held off, and this gives pilots a feel for the ground while looking outside.

 

Those problems with coffin corner and absolute ceiling could easily be experienced in the aircraft without risking aircraft as long as the pilots are disciplined.   Of course, insurance and bloody do-gooders would spoil that if we allow them to dictate terms, and that would take real guts to resist.  

 

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I reckon the most stressed lesson in glider training is " safe speed near the ground" and this means 150% of stall speed.

Gusty conditions and stol planes can make this too low a speed. Imagine a 30 knot stall speed, a 20 knot headwind , a 10 knot ground effect and a 10 knot gustiness.

The formula says approach at 45 knots. It is easy to see a stall surprising the pilot huh. The 45 knot reduces to 35 knots due to descending through the ground effect and then a lull due to gustiness reduces it to 25 knots...

 

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Don't you see 150% of stall speed while trying to land as a potential problem too Bruce?

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You need a fair headwind to get much shear so it's usually OK to carry something extra. Some formula's use half of the headwind and all of the gusts. That would pretty much cover your situation, Bruce. It's more of a problem with unpowered planes as the only way to increase speed is dive and if you aren't overshooting you can't do that or you don't reach the runway. Nev

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Yes your formula is better Nev. And Manwell, a glider has great big airbrakes and is easier to land than a Jabiru.  Also, the circuit can be at any old height in a glider since those airbrakes can fix just about anything. As long as you don't run out of energy.

One overcast day at Gawler some bored young solo guys had an unauthorized contest to see who could be highest over the fence and still stop short of the piecart. The winner was in a Hornet with 1500 ft.

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2 hours ago, Bruce Tuncks said:

Yes your formula is better Nev. And Manwell, a glider has great big airbrakes and is easier to land than a Jabiru.  Also, the circuit can be at any old height in a glider since those airbrakes can fix just about anything. As long as you don't run out of energy.

One overcast day at Gawler some bored young solo guys had an unauthorized contest to see who could be highest over the fence and still stop short of the piecart. The winner was in a Hornet with 1500 ft.

Thanks for the info gents.  I can see if you have "great big airbrakes", carrying excess speed wouldn't be a problem.  In slippery powered aircraft though, carrying an extra few knots for mum and kids ends up putting pilots in the danger zone of low and slow for longer, which increases the risk of an untidy arrival, rather than reducing it.  The listed approach speed already has a safety factor built in, and the more conservative pilots become, the more likely they'll end up coming unstuck.  I know this sounds counter-intuitive, but think about it like this - if you try to insure yourself against accidents by taking the easy way too much, you'll never develop the skills needed in a real emergency and won't be able to handle it when the inevitable happens.   This was illustrated in James Reason's Swiss Cheese model of accident causation, where there were two slices of Swiss Cheese with holes in them, and all that needed to happen was for one of the holes in each piece to line up for an accident to result.   It was also contained in the old adage about pilots starting their career with 2 cups - one empty, and the other full.  The full cup was filled with luck, and the empty one was for experience.  The trick is to fill the cup of experience before the cup of luck runs out, and that doesn't happen if you avoid improving skills.  There was another old saying about the superior pilot uses his superior judgement to avoid situations requiring the use of his superior skills, and that's true too!

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Carrying "extra for mum and the kids" is usually done by lazy, nervous pilots and not necessarily JUST low hours pilots. it's a creeping BAD habit. Your Target threshold speed should be chosen (and adhered to) based on the existing  conditions.. Any extra should/must be for a justified reason..

 A glider is possibly the only plane you (can) approach and flare with spoilers extended. They operate both in the air  to slow down and increase sink rate and to keep the plane on the ground after contact .

  In the Early 60's when tri gear became the norm and secondary airports had (longish) RUNWAYS rather than all over where you COULD land completely into wind quite a few wheelbarrowing incidents happened writing off a few Light aircraft. These were due having the nosewheel carrying aircraft weight rather than the mains. This could happen on take off or during the landing roll IF weight is not kept off the nosewheel. Also landing too fast and pushing the plane into the runway nosewheel first is a  common enough cause.. Nev

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On 30/09/2019 at 12:56 PM, facthunter said:

Ground effect does help but don't count on it. Picking a wing up with rudder is a great theory but at that point you are in a touchy situation, especially when low and with some mis-rigged planes. I used to fly a pretty rough Auster (because it was cheap) which would always end up rolling to the right at the ultimate point of stall regardless of how wing low to the left you were holding it with aileron and/ or left some rudder. .. By various means ONE learns  if you are lucky enough to survive. Practice  and more knowledge, makes you more lucky. Nev

I can’t believe that bit about the Auster, Nev 🤭

 

Mine seems to be rigged pretty straight and it will roll left or right with just a tad of rudder. Very simple stall recovery.

 

i always try to land on grass if available and my turn onto final is often around 40-45 knots with the barn doors open to minimise touch-down speed (a few ruts and things from mowing when wet). I slip in the turn and avoid bottom rudder like the plague.

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7 hours ago, Bruce Tuncks said:

Yes your formula is better Nev. And Manwell, a glider has great big airbrakes and is easier to land than a Jabiru.  Also, the circuit can be at any old height in a glider since those airbrakes can fix just about anything. As long as you don't run out of energy.

One overcast day at Gawler some bored young solo guys had an unauthorized contest to see who could be highest over the fence and still stop short of the piecart. The winner was in a Hornet with 1500 ft.

I loved the hangar run at the end of the day...zipping along a foot off the ground at 50 kn, then a left wheel off the taxiway onto the hard stand. Judging the energy so that you arrived sans braking.

 

are you going to Clare Valley fly-in, Bruce?

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