Cows getting bigger

Why the aggression? My only derogatory point was that a pilot with a degree of experience, especially unlimited aeros, should be able to 'feel' the aircraft without looking at the ASI. Adding a few knots to 'avoid the problem' doesn't exactly give me a warm feeling.

PS. Every 182 I have ever flown has most definitely told me it is unhappy when approaching CLmax.

n5296s

You guys are just amazing. The comparison with the Cessna Pilots Association, where I posted the same thing, is extremely illuminating - there it has resulted in a friendly discussion rather than the sh1tst0rm of people trying to prove how superior they are which has happened here.

I did this in my TR182. I said so. It is NOT an aerobatic aircraft. I also did not stall it nor get anywhere close. I said that too. The means I used to not stall it, was to calculate the theoretical stall speed, then add a generous margin. Generous enough that the stall warning did not activate, except briefly from time to time. That would be my first indication. The second indication would be mushy controls - and they get VERY mushy on the 182, close to the stall. There is no buffet to speak of. But the 182 (mine away) has a very docile stall if you enter it gently.

As they say, the superior pilot uses his superior judgement to avoid being obliged to use his superior skills. My judgement here was to give myself enough margin above the stall that I wouldn't NEED to be feeling my way at the edge of a stall - which I'm quite capable of doing, thanks very much. Just I'd prefer not to at a couple of hundred feet AGL. I'd prefer to have my personal limit for the turnback be a tad higher so I don't have to do that. (My guess is that flying on the hairy edge of a stall might give you another 50 feet or less - not worth trying).

n5296s

Depends what you mean by "unhappy". You could fly mine all day long just slightly below the indicated stall speed (well, not actually, because the engine would overheat - but the airframe would be fine with it). The controls are very mushy and you have to fly very delicately - but that's what you'd expect. I guess that's a reasonable definition of "unhappy". But it's perfectly doable. Just I'd prefer not to be doing it that close to the ground.

24Carrot

I will probably regret joining this thread...

For "angle of bank" above, substitute "angle off the vertical".

The vertical component of Lift has to match the force of Gravity, otherwise you accelerate downwards. If you tilt Lift off the vertical, you have to increase the load factor to avoid a downward acceleration.

Obviously if you bank the aircraft, Lift comes off the vertical and you have to increase the Load Factor. This is because, for practical purposes, the Lift Vector is at right angles to a line going through the wingtips.

With wings level, and a steady rate of descent, the Lift Vector tilts forward off the vertical. This is because the Lift Vector is by definition at right angles to the direction of travel though the air. This requires an increase in the Load factor, to avoid downwards acceleration, for exactly the same reason as the bank did.

If you bank and descend, you have a combination of the effects. An exact formula depends on some tedious definitions (the order in which you rotate things makes a difference), so suffice it to say that in a non-accelerating descending turn, the Load Factor has to increase because of both the bank angle and the descent angle.

n5296s

I don't think so - though I'd be happy to see why I'm wrong.

If VS is constant - whether zero or 20,000 ft/min - then by definition acceleration is zero and hence net force is zero, i.e. downward force due to gravity (mg) equals upward force due to lift. And hence lift perpendicular to the wing surface = mg/cos(angle of bank).

This ceases to be true as soon as VS isn't constant, of course. During the initial pushover, VS is accelerating downwards, so stall speed is actually lower. Where things go horribly wrong is when the pilot sees the ground approaching too fast and pulls. Now, the lift force increases and AoA may well go beyond the stall point. There are several horrific videos on youtube etc of airshow loops where this happens - the pilot is too low, pulls harder, stalls, and the aircraft pancakes into ground.

(Edited)

OK, I see your point now about the angle of the wings in the pitch plane. It's a valid point but in the noise mathematically. Suppose the aircraft is 5 degrees nose down. cos(5 degrees) is 0.996, i.e. less than a 1% difference. Suppose Vs=50 knots, in a 45 deg banked turn, stall speed is 59.46. With the correction for pitch attitude, it becomes 59.57. Of course there are numerous pilots on here who routinely fly airspeed to within 0.1 knot, I know I will be told, but I'm willing to humbly admit that I can't.

peterh337

Constant VS = constant G.

The only way to unload the wings, in a turn or in straight flight, is to accelerate towards the ground.

It's a good technique for doing really tight base to final turns. You just need plenty of air below you

mm_flynn

The angle of pitch has exactly the same effect as the AoB (if normally quite a lot smaller).

Put your elbow on the desk and hold your hand straight up - this will be the lift vector and the height of your hand will be the vertical component (which must equal the weight of the aircraft if it is not changing vertical velocity).

Now roll your arm left and right and note how the hand is closer to the desk (i.e. reduced vertical component). This works exactly as described in many earlier posts.

Now move your arm forward and back. This is what happens when you change pitch (you can see the reduced vertical component in this as well).

Finally if you rotate the arm and move it for/aft you have even less vertical component.

Normally we ignore this because even a 15 degree deck angle (which is going to be going down at 1600 fpm in a 60 knot turn (giving only 19 seconds to get the turn in from 500 feet) is only going to add 5% or so to the stall speed due to reduced vertical component of lift.

I would suggest in this discussion it can be reasonably ignored as well

Mark1234

Possibly futile, but perhaps if I explain what *I* meant further, noting that I specifically mentioned that I did/do not consider EFATO 'steady state':

A few years ago I played with the same problem in the R2160 - the posts may well still be available. Without using too many words, my best results were obtained by simply rolling to a large (60+) bank from the climb and pulling to buffet. Because of the excess bank angle the nose falls. In the course of the turn you go from a decent climb attitude to a best glide attitude and reduce the AOB somewhat to control the pitch. It's anything but steady state in either plane.

Pushing to best glide *then* turning wastes a bunch of energy and distance travelling in the wrong direction. (IMHO)

n5296s: I already admitted in the deleted thread that my initial comments were a little terse. My followup was more explanatory, but interpretation is equally down to the reader - written word lacks nuance; it is often worth clarifying what people mean. Insulting people who disagree or question you isn't generally a winning tactic, but at the end of the day if you wish to consider me a wannabe, your call..

BackPacker: Thanks for the reference I may have switched types, but I suspect your flying has outstripped mine these days.

Big Pistons Forever

One telling point is missing in the whole "turnback" discussion. Practicing it is just not the same as a real failure because you know the engine is going to fail and the "Oh ****" moment that happens with the unexpected real failure almost invariably results in a slower and initially less than optimal response.

Thus I think there is a danger of unrealistic feeling of attained competence in this manoever. I think it is also important to point out the powerful ground rush you get in a steep banked turn close to the ground. If you are not practiced in low level flying there is an almost irresistible effort to pull back on the stick which is why I think there is a prevalence of stall spin accidents with turnbacks. Practicing turnbacks at altitude is just not the same and again fosters a false confidence.

Secondly regular practice would obviously be required to maintain proficiency. For the average private flyer I think there are better things to practice then a manoever that covers a danger, the EFATO, that spans maybe 2 minutes of every flight. Pilots aren't bending metal on a regular basis because of EFATO's they are loosing control while landing, running off the end of the runway, etc etc. The less sexy but important fundamental skills are of more value practicing IMO.

n5296s

My whole point in the original post was a discussion about the technique, and I'm delighted that maybe this is finally turning into such. The theory says that 45 degrees is the best bank angle, but there's no substitute for getting up there and trying it out. If 60 degrees (or any other angle) works best (in some type, for some pilot), it's pointless to argue with that.

For sure the entry is anything but steady state (and btw I don't THINK I said that lowering the nose and turning were sequential, and it's certainly not what I did - 100% agree on that point). But once you've got it set up, it's just a question of holding the bank angle and pitch as accurately as you can, and waiting to get back in line with the runway. It would be kind of boring except it doesn't last very long and the proximity of the ground adds a certain tingle to it.

I'm always happy to be disagreed with and questioned, I expect to learn something from it. (For example, I do confess that I hadn't thought about the impact of pitch attitude on stall speed, tiny though it is). It's being patronised and nanny-knows-best-ed that drives me to irrationality. It's undoubtedly a character defect, but, well, you know, that's the way it is. imho it beats being a sheep.

Anyway, nice to see this turning back into a discussion. This forum has mostly been fairly well-mannered (though Peter would probably disagree) - unlike Rotorheads, which is a snakepit waiting for the unwary to tread - I don't post there any more. Fwiw, here's what I wrote first time around (slightly [edited]):

BackPacker

A number of previous posts revolved around this issue: How to reconcile the vertical component of lift with gravity, so that vertical acceleration is zero.

The missing link is not in tweaking the lift vector, but in the fact that there is now a vertical component to the drag vector. And since engine power is reduced (or absent, in the EFATO scenario) this vertical component of drag is not offset with the (downward) vertical component of thrust.

In the very extreme case, for instance a skydiver free-falling at terminal velocity, this is the only force that keeps the skydiver from accelerating vertically. (In other words his vertical speed is constant.)

peterh337

Would I ?

With very few exceptions, p p r u n e is OK. It is not cliquey, which is a big plus. And it has a good spread of expertise.

Croqueteer

Apart from an airbus all aircraft have an angle of attack indicator. It is called the control column. If it is further back than a certain aft position the wing is stalled. You can work out that position for your own aircraft.

abgd

I believe that may be true for equilibrium flight, but not for the sort of dynamic situations we're talking about, and then only for given CoG and power settings.

I would expect that method to bite you, sooner or later, if you depended on it to do a steep turn at low level. And if it were so reliable, why would aircraft be fitted with stall warning tabs and AoA indicators? It would be much simpler to put a gauge on the control column.

Pilot DAR

........As long as you account for the possible affects of power, flap position, landing gear position, different undercarriages, C of G position, ground effect, wing contamination, STOL kit, and G load.

I'd rely on the functioning stall warning system of the aircraft, and the skills and "feel" associated with competence and currency in that aircraft type.

foxmoth

Being an aerobatic aircraft has nothing to do with it - you are not doing aeros, the trouble with flying a set bank angle and speed is that your head is not where it needs to be - outside the aircraft, set the bank angle and speed and try and fly these with your head outside - either the bank angle increases (stall/spin) or the speed reduces (stall/spin) or both, if it goes the other way (bank angle decreases or speed increases) you probably will not get round the turn. fly head inside and you do not see where you are properly in the manouver -not a good idea that near the ground, plus of course the idea is to get to a workable piece of ground, wings level and enough speed to flare, if you are concentrating inside you could well miss this as well! This is why you want head outside, and to be able to pull by feel.

24Carrot

n5296s:
mm_flynn:
If you are comparing scenarios, I would include it, but I agree it is probably not a major feature. FWIW with a "L/D ratio" of 8, and a 60 degree angle of bank, I get a theoretical descent angle of about 14 degrees.


Backpacker, you are of course right, there is a vertical component of drag in a descent. In mitigation, sometimes I only come on pprune every few days, and I had missed the earlier thread completely. Sorry for the missed or repeated points!

mary meagher

All levels of expertise welcome in this discussion? OK, here's my thoughts on turning back after engine failure; which I think you are discussing under the title of "the impossible turn".

Rather important to keep up your speed in a low level turn in a tight situation, for all kinds of reasons; probably turbulence near the ground, wind gradient, are problems that are solved by a reasonable increase in speed over normal stalling speed. We practice "engine failure after takeoff" all the time in gliding, only it's called a cable break, or winch launch failure. Half way up the launch comes the "o ****" moment, when at a terrific angle relative to the ground, suddenly the PULL that has lofted your aircraft at a happy flying speed into the relative airflow, QUITS! and you are left hanging there, nose very high indeed!

The routine that follows: LOWER THE NOSE TO THE RECOVERY ATTITUDE. This is rather lower than the normal flying attitude. WAIT for the ASI to INDICATE correct speed to fly a circuit. IF YOU CAN SAFELY LAND AHEAD, LAND AHEAD. If not, turn AWAY FROM WIND, and when you have completed the turn,( at a safe speed but not throwing height away by excessive speed) you will be presented with a selection of IN TO WIND approaches. This can all happen in about 30 seconds, and when you are well experienced with launch failure, 30 seconds feels like all the time in the world.

The lifesaving part of this routine is establishing the PRIMACY of the decision to LAND AHEAD. Always the first choice. I don't want to go into the unhappy history of what happens if that first choice, a safe landing ahead, is ignored for reasons of convenience or a desire to return to base. It really doesn't get practiced properly, in power flying.

I'm sorry, I don't understand anything at all about tweaking lift vectors, constant vertical speed or load factors. But I have had plenty of practice in launch failure, stall recovery, safe low turns, and always having a plan B.

n5296s

For what it's worth, or maybe because I'm just a glutton for punishment, I did some follow up experiments on best speed and bank angle. They're posted over on the EFATO thread.

BackPacker

Actually in my gliding training, it was hammered into us to call out "50 meters, safety altitude" and "100 meters, abbreviated circuit" out loud. Loud enough that the instructor in the back could hear it, at least. In the power world you'd do essentially the same thing but call it a departure briefing.

Up to 50 meters your nose-up angle should not exceed about 30-45 degrees because otherwise there's not enough time/energy/altitude to establish a normal final glide/landing attitude if the cable breaks. Only above 50 meters were you allowed to pitch higher than 45 degrees. (60 degrees or so is very common at that stage of the launch.)

Above 100 meters (and due to altimeter lag, in reality it's more like 130 meters at that point) you have sufficient altitude to fly an abbreviated circuit. But what's more: You are probably so well progressed over the length of the field that landing ahead in the gliding field is no longer an option. Even with powerful airbrakes, the descent angle required to make the field is simply not achievable. Of course an outlanding in the next field is still possible but why would you if you have sufficient altitude to return to base?

My first simulated cable break was at 100 meters. I knew that in theory I could make it back to the field with an abbreviated circuit but this was the first time in real life. So I did not dally, dropped the nose immediately while turning straight onto downwind. An immediate pre-planned action like in EFATO training. My instructor had to slow me down and actually had to use the airbrakes on downwind to lose an extra 20-30 meters or so, to make it "interesting" (his words). And even then we still had plenty of altitude to setup a decent final approach.

(Dutch gliding is in metric, for some odd reason.)