Turns at low IAS

[old man emu]

I'm considering starting another controversial thread, but I need some clarification, please.

 

When flying circuits, where is an aircraft most in danger from a stall/spin incident?

[Thruster88]

On  climb following engine failure. So up wind or cross wind.

[old man emu]

Can we leave the engine failure scenario out? I know it happens, but that's taking the starting point of what I would like to discuss a step beyond where I want to be.

 

I'll take your response and restrict it to "On climb, up and/or crosswind", if it's OK with you.

 

Is there a danger in turning from downwind to cross wind in descending flight at low speed?

[Thruster88]

There could be a danger turning down wind to base or base to final but as an avid reader of ATSB accident reports it is not on the radar, I can't think of one from memory not involving engine issues.  

[Jabiru7252]

From what I have read, it's turning finals. You're low and slow, you're focused on the aim point, you overbank to try to not overshoot the centre line then you're in trouble...

[facthunter]

Turning onto final. You have a definite centreline to be on and if there's a downwind on base you might be tempted to tighten the turn by "ruddering" it. It's also the place where you're most likely to get involved  with other traffic, including one pulling out on you  on late final, and you are on a limited distance to a touchdown point, so you have defined your descent path. Your final approach has to be right . Nev

Edited January 7, 2021 by facthunter

[old man emu]

Let's keep it simple. The circuit is at Old Mate's place at Wattagai.

[Thruster88]

Ok there was this one. https://www.atsb.gov.au/media/news-items/2020/stallspin-accident/

 

I hope we are not going into some long winded dodgy mathematical bs. It would be more productive to talk about the human factors that led to pilots not maintaining a proper airspeed. Distraction? 

[facthunter]

I don't think you'd have to do too much searching. . Turns at LOW speed. Sounds hazardous. I watched a C-172 do high voltage powerline inspection in the 90's and said to my wife. "He's not doing that very safely" . Next day I heard he'd crashed and was  killed. ..

    Any turn has a correct speed, done at a safe margin above stall for that plane with it's load and bank angle and amount of flap extended. IF you tighten the turn or have the ball off centre, you start to rely on luck. Distraction is often a factor.  I've been in a situation where I had to stay in ground effect to execute a 180 degree turn to avoid rising ground. IF you're smart, you don't get yourself into that  position. I've used ground effect a few times but you are pushing the boundaries. Croppies probably do it often. Nev

[old man emu]

1 hour ago, Thruster88 said:

I hope we are not going into some long winded dodgy mathematical bs.

When have I ever done that!!!???

 

I think we could end up riding on the rim of a two-sided coin. The mathematics tells us that it's going to happen, while the Human Factors lets us ask why does it happen to people who have been shown the mathematics. One side of the coin is objective and can be show mathematically within a virtual reality as well as practically in reality. The other side of the coin is subjective and the results of any test cannot be replicated exactly, only "on average". The subjective side deals with human psychology where "All the world is queer save thee and me, and even thou art a little queer." --Robert Owen, 1828

[facthunter]

IF it's explained and still they don't understand, It's not been explained very well. They could also be of a careless disposition. Of course in a car you don't fall through the road surface when you drive slowly or stop, but they say anyone who can drive a car can fly a plane.  Perhaps they were only kidding and wanted the money.

  Perhaps they don't "get" the dynamic in aerodynamic. Nev

[Jase T]

5 hours ago, old man emu said:

I'm considering starting another controversial thread, but I need some clarification, please.

 

When flying circuits, where is an aircraft most in danger from a stall/spin incident?

when trying to intercept the runway centerline after overshooting the turn onto final... With flap out and engine at low RPM. Pilot is looking out trying to get it right.. Using a lot of AOB and a bit too much rudder, not paying attention to the airspeed as the eyes are concentrating on the linup.. Airspeed gets low...

[SSCBD]

OME - Let's keep it simple. The circuit is at Old Mate's place at Wattagai.

 

So why is everyone looking to fly low slow on base final turn? Because we were trained that way on L plates.

Simple way out of it - is to extend you normal downwind by 20 to 30 seconds - at cruise speed for RAA or not over 100kts do your landing checks without slowing down.

Next when you are ready at extended base, do radio call base with long final, with that out of the way -   then turn, kill rpm and turn basically a continuous 180 degree turn onto final. Stop worrying about an extended center line if you miss it just drift back on it with a bit of rudder,  Just don’t pull the nose up doing it.

When on long final then lower flaps and trim out for control of airspeed. Add power if needed but you will be basically be on a long final to clean everything up if needed and maintain airspeed with power or not.

Note

However, I do miss the old big ASI when flying glass cockpits as it always takes me longer to get and accurate read on the ribbon type airspeed with my head inside not outside the cockpit – with the old steam gauge it just a eye flick at the needle and am happy.

 

Hope this all makes sense – no need to push tight circuits – enjoy the flying and take the pressure off yourself and makes it safer.

[Roundsounds]

Having spent thousands of hours flying with many pilots of varying levels of experience, my observation is the turn from base to final has the greatest risk.

The tendency to skid that turn is greatest, I believe this is due to;

- minimising bank angle during the final turn, resulting in an overshoot

- overshooting final sees most pilots overdo rudder use

The increase in drag due to the skid results in a bleed in airspeed, the combination of skid and decreasing airspeed can be fatal.

[skippydiesel]

I have no memory of being concerned about turning final during my GA days. The mainly Cessna 172's I flew, just seem to be so well behaved, maintaining speed an attitude through turns with ease.

 

Now that I am RAA and fly a much lighter/low inertia aircraft, I have become very much more aware of turns at low speed,  as even a slight loss of concentration can see the nose rise during this turn and corresponding sharp drop in air speed.

 

So it would seem to me that the warnings/teaching I received in GA about air speed/attitude, when turning final, now have some real meaning in the LSA world.

 

Not suggesting things cant go wrong in GA, just that the typically heavier aircraft, are lese likely to exhibit the sudden loss of air speed that an RAA aircraft can so readily show.

[spacesailor]

On one aircraft . HBird, the fuel tank is over your legs, Nose heavy on take-off. ( full fuel )

BUT

tail heavy on landing, ( fuel used )

No-ones said anything about that, but it must make some difference when on finals.

even if the CoG is still within tolerances, ( forward on take-off. Rearwards on landing )

easier to stall with empty fuel tank in the front.

spacesailor

Edited January 7, 2021 by spacesailor
added more

[Jabiru7252]

SSCBD - I tend to keep my circuit tight. If the rubber band breaks I can glide to the strip. If one has to drive the plane in on final and the rubber band breaks, they are %^$#ed. 

[cosmicray]

I think the root cause of many stall / spin accidents when turning final is an over reliance on power during approach. Dragging the aircraft through a shallow approach using large amounts of power as routine is asking for trouble. Keeping the circuit tight and the final turn high enough so that you can glide to a landing in the event of engine failure is common sense but it seems not so common. 

[facthunter]

A powered approach is advantageous in Gusts or when using a minimum length strip. POWER is another control if you choose to use it. A low dragged in  power approach is just poor technique and often a misjudgement that reduces safety.  Power is essential in very strong headwinds or the approach path would be absurdly steep. SOME power means faster  and more reliable response if power is required to go around or manage downdraughts.. Large amounts of flap produce a lot of drag for the lower speed desired and the "sink" rate unpowered would be unmanageable, unsafe and outside Undercarriage  design parameters.  Nev

[old man emu]

18 hours ago, skippydiesel said:

much lighter/low inertia aircraft

Now that's something I'll have to address - inertia.

 

So far my research has introduced me to:

1. Angle of bank and its relation to stalling
2. Angle of Attack in climb and descent
3. Radius of turn in relation to speed and angle of bank
4. Now Inertia as it more greatly affects low mass aircraft.

I'm interested to study the Procedure Turn principle for doing a 180 degree turn to reciprocal heading

As I said, I'll avoid Human Factors, but welcome someone else starting a sister thread to deal with HF and Stall/Spin.

 

 

However, as i delve deeper into this Lift thing, I am being swamped with the number of variables that can affect the creation of Lift. It's a wonder that a plane can fly at all.

 

 

 

[facthunter]

True .It has absolutely no feathers, but if you look at model aircraft, anything at all can fly if the motor's powerful enough.. Nev

[old man emu]

We are all a bit weird in our own ways. I like to look at the physics of flying and much of the rest of the math-based stuff. The mathematical descriptions associated with flight should provide a simple answer to the question "How does a plane fly". Unfortunately, at every twist and turn there are additional variables to complicate the answer.

 

I'm coming to the conclusion that the answer to the question is, "Because they do." For the majority of pilots that's answer enough in relation to the Theory of Flight. For that majority it is the practical aspects of flying that are paramount. Flight instruction should be based on "If you do this, you will have a safe flight. If you don't, you die."

[Garfly]

OME, in my humble opinion, you sell your research efforts short if, finally, you settle for 'because they do'.

Whether a pilot needs to know the whys and wherefores or not, curious folks don't need to give up on it (even if aeronautical engineers seem confused).

This video lecture suggests that they are not confused, actually; it's just that the physics of lift is too complex to reduce to simple intuitive explanations. Personally, I'm satisfied with this engineers attempt to clarify the issue.

(Spoiler alert: Aircraft create lift by turning the incoming flow downwards. Not so complicated an answer, after all.)

 

 

Edited January 8, 2021 by Garfly

[facthunter]

That's ALL you need to know. Push the air somewhere and it pushes you the opposite way. Another clue. When the flow is curved, there's always higher pressure on the outside of the curve  (otherwise it wouldn't bend). Airfoils or weather systems work the same , but the rotation of the earth affects the eddies in weather systems. The direction of rotation around highs (or Lows) is reversed in opposite hemispheres. Nev

Edited January 8, 2021 by facthunter

[pmccarthy]

Who can tell us about wing designs? I know little about them, except most wing cross sections were designed in the early 1930s and we just choose one of them. It must be more complicated.