Learning to fly, or thinking of learning? Post your questions, comments and experiences here

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By TopCat
FLYER Club Member  FLYER Club Member
#1884191
T6Harvard wrote:New technique was pull the power as soon as we were over runway then back pressure to flare and hold off. Didn't work for me. Invisible ratchet works for me, both power and back pressure being worked in tandem, although obvs power is off just before last of the hold off.

Hmm. I actually approve strongly of that technique :)

At some point, you absolutely will need to learn to land without the comfort blanket of having a trickle of power on to slow the descent. With glide approaches (which you eventually want to do lots of, as practice for engine failures), there's no power available and you will be learning them, so "didn't work for me" won't be available forever - you'll need to make it work.

I'm not saying that point is now - slowing down the descent so that you get longer to see what's going on is not a bad thing in the early days, but that point must come, and the sooner the better.

Also, the invisible ratchet has nothing to do with whether you've got any power set - it's about gradually increasing the back pressure as the speed bleeds off, and if done right in calm conditions, the back pressure is only ever increased, not decreased, hence the analogy with a ratchet, which only turns in one direction.

It's a useful concept, but in the real world with gusting winds it's not always possible to apply it completely.

I was too fast, no headwind to dissipate air speed

Hmm again. Do you actually mean that? There is a subtle sense in which it's true, but (no disrespect!) I'd be surprised if it's what you meant :)

More later :)

Disclaimer: I'm just some guy on the internet. Do what your instructor tells you, unless of course he's rubbish :)
By TopCat
FLYER Club Member  FLYER Club Member
#1884207
T6Harvard wrote:So now you can see why I'm not progressing! :lol: :roll:

Er, yes you are, very much so!

Still making the effort though :D

:thumright: :thumright:

I'll ramble more on the subject of power and landings later.

And headwinds. As homework, figure out the answer to this:

You're in a hot air balloon, not changing height. The wind at your height is a steady 5 knots from the north.

You light a candle. Which direction does the flame point, and why?

Smart alecs that already know and understand the answer please don't reply - students only please.
By Duncan M
#1884236
T6, 4 week gap in lessons is quite a lot, so I wouldn’t get too concerned at progress.
The place and time to sort out the landing is in the hot seat with the flight instructor.
In that spirit I offer a few thoughts:

1. Think carefully about airspeed. It is the speed the aircraft is moving through the air.
It has nothing to do with groundspeed. It an extreme case you could have IAS of 60kn
with a headwind of 60kn. In theory then you could climb vertically over the same point
on the ground. Your ground speed in this case is zero.
If you then turned around with a tailwind of 60kn and IAS of 60kn your speed over ground would be 120kn.
The groundspeed is what you deal with when the wheels are on the ground. Landing into a headwind reduces your groundspeed making ground handling easier.

2. The reason for ballooning is pulling back on stick too far for the intended flight path.
If the aircraft has a lot of energy (speed) pulling back on the elevator will increase pitch and lead to a climb......ballloon.
The solution is as you’ve already said in your post.
When I was driving ships, and had a critical turn in confined waters I used to apply a small amount of rudder
(known as “warming the bell”.......don’t ask why!) in the direction of intended turn. This got ship moving in correct
direction before the full rudder was applied. This is similar to your invisible ratchet, where applying a small amount of elevator ( NOT RUDDER!) at the start gets the aircraft moving from descent to level flight.

3, In the transition phase from descending to level flight and then to the landing attitude,
you need outside reference. Looking ahead down the runway works until you balloon
and can no longer see your references. It may be that looking to the side will get that reference back.

Good luck for next lesson.
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By jcal
#1884255
T6Harvard wrote:Well I have another string to my bow....I can balloon :roll:

You haven't ballooned until now?! :shock: My first 10 landings were all probably balloons :lol: :lol:, from small to big ones.

I think my struggle with the power off technique when learning it (which is the only one we use really) was how suddenly it felt like the aircraft was going to just slam into the ground, so my fear-of-death reaction was to pull back too much and hence ballooning. It took me a few attempts to realise it was mostly just a feeling and in reality I had plenty of time to ease the aircraft onto a level flight over the runway.

Really had to train that instinct away! I found it a hard thing to do and I still struggle occasionally.

Milty wrote:It’s surprised me how much a break in training can have an impact.

I found that it can go both ways! Having a nice break after a few "bad" lessons can make a huge difference once you get back, at least that's something I found! But I do try to keep it regular, once a week if possible.
T6Harvard, Milty liked this
By Harleyatrix
#1884294
Hello T6Harvard
I’ve been lurking for a long time & following this thread.
I’ve just activated this my account on Flyer & will attempt to send you a message.
User avatar
By T6Harvard
FLYER Club Member  FLYER Club Member
#1884317
Harleyatrix wrote:Hello T6Harvard
I’ve been lurking for a long time & following this thread.
I’ve just activated this my account on Flyer & will attempt to send you a message.


@Harleyatrix , I think you can't pm when you are a brand new user. You maybe have to make a few posts. I'll wait :D
By TopCat
FLYER Club Member  FLYER Club Member
#1884585
Ok, as promised, here are some thoughts on this thing about flaring and holding off with and without power on. It's a bit of an essay, sorry. As ever, I'm just some guy on the internet, your instructor is the one in charge, blah blah.

BTW, when I say 'with power on', I mean a little power on in the flare and hold-off. There is one situation where you might keep quite a lot of power on, but I'll come back to that. I'm talking about normal landings for now. I'm also talking about normal training aeroplanes, not exotic types that need different techniques. I don't know anything about those.

There are advantages and disadvantages of keeping power on in the flare and hold-off. Advantages first:

Because you still have some thrust, the airspeed will decay more slowly. This gives a more gradual loss of lift, so you can afford a more gradual application of back pressure (and hence increased angle of attack) to compensate. So you have more time to see what's going on as the aeroplane descends through those final few feet. For low-hours students, this can be very helpful, as until you've had a reasonable amount of practice, it can all happen in a bit of a blur. And as we've discussed, you only get about 10 seconds of actual landing per circuit.

Actually, this is the only advantage I can think of.

With power, you also get a flatter approach, requiring a smaller pitch change in the transition to the hold-off, but I don't think that's an advantage.

Disadvantages:

  • It doesn't help you learn glide approaches, which are essential to practise in case you get an engine failure one day.
  • It doesn't help you land if the runway is short. Taking longer to slow down means you will touch down further down the runway.
  • Touching down further along increases the temptation to land flat just to 'get it down'.
  • If you're having to coordinate gradual power reduction during the flare and hold-off, as well as gradually increasing the back pressure as the speed decays, that is more work than you need. In the last few seconds before touchdown, especially if it's gusty, the last thing you want is more stuff to do, and have to do it for longer than you need.


Much better IMO is to close the throttle completely once you know that you can make the runway. Keep your hand on it (you might need to add power promptly if you get some unexpected sink), but unless you need it, leave it shut.

Then, concentrate on the flare and hold-off. It will happen quicker, but you'll still get used to it.

Early on, because things are happening faster, there will be the temptation to panic a tiny bit, and subconsciously add larger control inputs. That's one thing that might account for ballooning when you closed the throttle on very short final. You just hadn't expected it all to happen quite so quickly, and overcompensated. That's all a balloon is - too much back pressure.

Without power, the last bit of the approach will be a bit steeper, so you'll need a bigger pitch change in the transition from the flare to the hold-off. If you're not used to it, it's easy to overcook it, especially if you're slightly stressed.

With practice, it'll become easier this way than when you were fiddling about with the power as well.


Why is it harder when the wind is calm?.

Suppose your approach speed is 60kt, and you're used to headwinds of, say, 10kt. You'll be used to approaching the threshold with a ground speed of 50kt. Then one day there's no wind, so your ground speed will be the full 60kt.

This has a number of effects. First, even if you stick to exactly the same airspeeds, you'll get to the threshold sooner (because you're going faster over the ground), and the flare and hold off will likewise use up more runway. If you're subconsciously used to increasing the back pressure when you have a particular visual picture, you'll be too early. If the aeroplane hasn't had time to slow down properly to approach speed, you could also be too fast.

With runway going past faster than you're used to, a few knots too much airspeed because you got to the threshold sooner than you're used to, it's easy to apply the back pressure too early and/or too much, and balloon upwards.

Solution:

  • More practice with the throttle closed on short final, and staying closed all the way through the flare and the hold off. Unless you need power of course - you always need to be alert to unexpected sink. But having a trickle of power on doesn't protect you against that.
  • More patience in the hold-off, even though the runway is going past faster than you're used to. If the hold-off is taking more time (as opposed to more distance), your airspeed is too high. Go around if you're running out of runway.


Does headwind affect airspeed at all?

Short answer: no. You're flying through a big parcel of air. The aeroplane doesn't know whether that parcel of air is itself moving relative to the ground, which it doesn't care about, even a little bit.

Longer answer: there are wind gradients, and usually the headwind close to the ground is less than the headwind 50' up in the air. So as you descend through a decreasing headwind, your airspeed will decrease. However, this doesn't affect the most important part of the landing, namely the hold-off. This is all at more or less constant height. The thing that the headwind affects is the ground speed, not the airspeed. When the ground goes past faster than usual, it looks weird, so if you're not expecting it, it can fool you.

Very short field landings

So, why would you ever want to have quite a lot of power on in the later stages of the approach? If you haven't got the hang of normal landings yet, you probably won't have encountered this. It's where you want to land absolutely as short and as slow as you possibly can.

For this, the last part of the approach will be quite a lot slower than usual. So the angle of attack will be quite a bit higher than usual, which will cause quite a lot more drag than usual. To counter this you'll need significant power, which, if removed, will result in a rapid deceleration (due to all that drag), and hence loss of lift and increased sink. The idea is to remove all that power just before touchdown, which means that you'll touch down almost immediately with virtually no float, with the nose well off the ground for maximum drag once down.

As you can imagine, this technique requires a deft touch, especially when it's gusty, and it absolutely isn't a gradual power reduction during the hold-off - it can require many power changes, some quite large, to maintain the airspeed at a margin above the stall that's much less than you're used to. And you absolutely have to be very awake indeed. If your airspeed control isn't good enough for this, don't blame me if you smack it into the ground.

This technique allows you to cheat at spot landing competitions, as the removal of the power means a more or less instantaneous landing (if you're at the right height. It's a crash if you're too high). Personally I think all spot landing competitions should be off a glide approach from no closer than the downwind/base corner :)
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By lobstaboy
#1884591
Good essay @TopCat
The thing about wind gradient near the ground can be confusing to folk who like to think about these things.
Why? Because in one breath we say the aeroplane is flying in a parcel of air and it doesn't know or care what it's ground speed is, just it's airspeed. And then we appear to flatly contradict this by saying as we descend through the wind gradient the airspeed changes because the wind is different.
The contradiction goes away if you include inertia in your picture of what is going on. Inertia means it takes a few seconds for the aeroplane to adjust it's airspeed (crucially by losing height more rapidly). Away from the ground if we fly through turbulence you can feel this happen - that's what turbulence is - but it doesn't matter. Twenty feet above the ground it does matter, so we have to be ready for it.
By TopCat
FLYER Club Member  FLYER Club Member
#1884843
lobstaboy wrote:in one breath we say the aeroplane is flying in a parcel of air and it doesn't know or care what it's ground speed is, just its airspeed.

We do say that, because it's true. In a parcel of air which is moving at constant speed, we can fly at a given airspeed in any direction we like, and the aeroplane has no idea that the parcel of air is moving. We can accelerate or decelerate, and that remains true, because all the time we're pushing against the air. Whether there is ground nearby is irrelevant, other than as a source of gravity.

And then we appear to flatly contradict this by saying as we descend through the wind gradient the airspeed changes because the wind is different.

There's no contradiction. If you instantaneously change the wind, the airspeed has to change just as instantaneously.

This shouldn't seem strange. Imagine an aeroplane flying along, minding its own business. Suddenly you stick a huge fan up blowing air towards the oncoming aircraft. Of course this suddenly accelerates the air over the wings, increasing the airspeed instantaneously.

Inertia means it takes a few seconds for the aeroplane to adjust its airspeed

This is true, but it's not the same change in airspeed that happened because the wind changed.

It takes time for the aeroplane to change its own airspeed by pushing against the air, and consequently accelerating in, and relative to, the parcel of air it occupies.

However, it remains the case that if all of a sudden you move from a parcel of air going at one speed, to a parcel of air going at another speed, the airspeed changes just as suddenly.

What does not change instantly is the velocity of the aeroplane relative to the space it occupies. It will start to change, for sure, because of the different forces it's now experiencing. So for example, consider the aeroplane from earlier, flying at 60kt in a 10kt headwind. We're doing 50kt relative to the ground.

If we fly suddenly into a patch of air where there's no wind, we're still doing 50kt through space (or over the ground if you prefer). Our airspeed is now 50kt, so if we don't mess with the controls, and leave the power alone, we'll pitch down (as we're trimmed for 60kt, remember) and (assuming for the sake of the illustration that the phugoid is well damped) the aeroplane will accelerate back to 60kt, and then we'll be flying at 60kt again, this time with a ground speed of 60kt.

Airspeed changes, both positive and negative, can be very sudden due to windshear. If you get a sudden reduction in airspeed near the ground, you may need to apply a lot of extra power very promptly, to accelerate the aeroplane back up to an airspeed above the stall.

You don't feel the change in airspeed (in fact you don't feel airspeed - or even ground speed for that matter - at all), of course, you feel the sudden descent (or climb, if it's a gust), because it's an acceleration. This is because at the instant the wind (and hence the airspeed) changes, the speed of the aeroplane through space has not yet had a chance to change, so you don't feel it as a (horizontal) acceleration through the seat of your pants.
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By lobstaboy
#1884847
@TopCat
Er, yes. That's what I said.
There appears to be a contradiction - implies there isn't really.
The reason the speed through space doesn't change instantaneously is inertia - what I said.
As always, read Stick and Rudder.
By TopCat
FLYER Club Member  FLYER Club Member
#1884849
lobstaboy wrote:There appears to be a contradiction

Well I don't agree with this. I don't think there's any apparent contradiction at all.

The first airspeed change takes place instantaneously when the wind drops.

The second airspeed change takes place gradually as the aeroplane accelerates itself back to its original airspeed.

They are two separate airspeed changes, and they happen for different reasons.

I understand that it's a shorthand, but I also hate references to 'inertia' as if they explain anything. Much better IMO is to talk about forces and accelerations. If you get the forces right, what the aeroplane does as a result is perfectly clear.
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By T6Harvard
FLYER Club Member  FLYER Club Member
#1884850
Thanks for taking the time @TopCat and @lobstaboy. It all makes sense. It's the physical doing that's the problem. Despite all my airborne hours I've not had that much experience, IYKWIM.

When I read your sentence Topcat, "Without power, the last bit of the approach will be a bit steeper, so you'll need a bigger pitch change in the transition from the flare to the hold-off. If you're not used to it, it's easy to overcook it, especially if you're slightly stressed", I thought again (again!) about my reactions. On a couple I think I undercooked, reacting as if I still had some power on and was descending slightly less steeply, and hence my Instructor intervened to stop nose-wheel first.... IDK.

Oh boy, I hope it all improves next week!

Tomorrow looks like a good day to fly the chair :mrgreen: I shall also devote some attention to the next TK exam, Aircraft General, so I can achieve something positive before Christmas :)
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