The Unforgiving (née Impossible) Turn.

[Thruster88]

29 minutes ago, walrus said:

 

You mean TRIM for best glide speed to leave yourself freer to do the rest.

No, use the stick to get to best glide speed, start the turn if that what you decide, live with the stick force or trim if there is nothing better to do with your free hand. My RV runs out of trim with just me and full flaps, it is not a big deal to fly with some stick force.  

[pmccarthy]

God point about the ASI. Perhaps it should be bigger and right in your face. It doesn’t get the prominence it deserves.

[kgwilson]

Trim for best glide if a) you have time and b) you have available trim. When I was training it was just nose down & best glide speed with EFATO. With engine failure at 4000 feet it was nose down & trim for best glide.

[derekliston]

15 hours ago, Thruster88 said:

Pilots and unfortunately their passengers die attempting the impossible turn because they STALL THE AIRCRAFT. while it may not be possible to return to the runway in some aircraft in others it is a viable option. Pilots also stall aircraft flying straight ahead following engine failure 

 

Reading emergency engine failure check lists for light GA aircraft there is limited or no advice to maintain best glide speed. It should be every second item on the list and said out loud by student pilots. Example

 

Engine failure on initial climb.

Best glide speed

Boost pump on

Best glide speed

Change tanks

Best glide speed

Carb heat on

Best glide speed

Mags left right both 

Best glide speed.

 

Also if a second airspeed indicator stuck up out the top of dash in line of sight like a bogans tacho more people would be saved. Eyes out front and airspeed info at the same time yesssss. Perhaps a line on the airspeed indicator called the line of death would help. Airspeed is life.

I have been seeing online ads for a GPS speedometer which would be ideal to sit on top of the panel. Unfortunately it can only be set for kph or mph. If it could be set to read in knots I would buy one.

[IBob]

41 minutes ago, derekliston said:

I have been seeing online ads for a GPS speedometer which would be ideal to sit on top of the panel. Unfortunately it can only be set for kph or mph. If it could be set to read in knots I would buy one.

What you are needing is an Air Speed Indicator, and GPS will absolutely not give you that: the last thing you need to be looking at to avoid stall is (GPS) ground speed........

[Old Koreelah]

5 hours ago, pmccarthy said:

God point about the ASI. Perhaps it should be bigger and right in your face. It doesn’t get the prominence it deserves.

In your line of sight is ideal, perhaps some sort of HUD. My preference is for a Reserve Lift Indicator like so many STOL people use.

[facthunter]

For a simple aircraft  an audible stall warning which actuates about 5 knots above stall will serve the same purpose. In critical situations, I've done this when I had to also keep my eyes outside the cockpit. Nev

[Old Koreelah]

Like this one, Nev?

[facthunter]

Yes Sir. Nev

[tcsmith]

Re impossible turn.

 

We included a turn back on takeoff in the gliders. using an IS28 aircraft, we would pull the cable release at 200 feet after training, from a 65 Kt Aerotow and initiated a medium turn back to the airstrip. This gave  experienced pilots a clear landing with no problems. Not for beginners. Dont try this with powered aircraft!!!  Cheers

 

Terry

[Roundsounds]

On 6/8/2022 at 6:15 AM, pmccarthy said:

God point about the ASI. Perhaps it should be bigger and right in your face. It doesn’t get the prominence it deserves.

IAS means very little as you load up in a turn.
You need to be able to establish a known attitude to establish the glide. Given power + attitude = performance you only need to know the correct attitude given there’s no power. 

[aro]

16 hours ago, tcsmith said:

Re impossible turn.

 

We included a turn back on takeoff in the gliders. using an IS28 aircraft, we would pull the cable release at 200 feet after training, from a 65 Kt Aerotow and initiated a medium turn back to the airstrip. This gave  experienced pilots a clear landing with no problems. Not for beginners. Dont try this with powered aircraft!!!

 

How long does it take to descend 200'? At altitude and without additional lift, how far can you turn in 200'?

 

The equivalent altitude in powered aircraft might be 800-1000' as a guess?

[facthunter]

Whatever your engine out approach  sink rate is applies and has to be increased when turning. The rate of turn V/S height loss determines whether you get there in a course reversal but there's a bit more to it. You turn more than 180 (say 220) and then another  40  back again to align with the runway. A very shallow bank is not the most effective because you cover a larger distance and take more time. Nev

[APenNameAndThatA]

On 29/8/2022 at 9:22 PM, Roundsounds said:

IAS means very little as you load up in a turn.
You need to be able to establish a known attitude to establish the glide. Given power + attitude = performance you only need to know the correct attitude given there’s no power. 

 When I practiced impossible turns at height, I would be climbing at Vy, close the throttle, wait three seconds to simulate fright, then start the turn. Because I was already slower than I wanted to be, and wanted to begin a tight turn ASAP, I dropped the nose well below the horizon, then began my turn, then started raising my nose. 

 

It would take a *lot* of practice to get that right relying on external sight picture, *and* the picture would be a bit different with idling engine vs stopped vs windmilling engine because the speed at different stages in the manoeuvre would change. I never really got around to establishing a glide because I was manoeuvring the whole time. 

 

You referred to establishing a glide. Well, if you are in cruise and the engine stops, you climb, gain height, and at Vy, establish the glide. You can’t tell from the airplane’s attitude when you get to Vy because you are climbing when it happens. 

 

Like the movie title says, IAS is everything everywhere all the time. 

Edited August 31, 2022 by APenNameAndThatA

[Roundsounds]

25 minutes ago, APenNameAndThatA said:

 When I practiced impossible turns at height, I would be climbing at Vy, close the throttle, wait three seconds to simulate fright, then start the turn. Because I was already slower than I wanted to be, and wanted to begin a tight turn ASAP, I dropped the nose well below the horizon, then began my turn, then started raising my nose. 

 

It would take a *lot* of practice to get that right relying on external sight picture, *and* the picture would be a bit different with idling engine vs stopped vs windmilling engine because the speed at different stages in the manoeuvre would change. I never really got around to establishing a glide because I was manoeuvring the whole time. 

 

You referred to establishing a glide. Well, if you are in cruise and the engine stops, you climb, gain height, and at Vy, establish the glide. You can’t tell from the airplane’s attitude when you get to Vy because you are climbing when it happens. 

 

Like the movie title says, IAS is everything everywhere all the time. 

You do realise there’s quite a lag in the indications associated with the pitot / static system fitted to light airplanes? This leads to people wasting valuable time chasing IAS and I believe leads to LOCi accidents. If you practice learning and  establishing glide attitudes for various types of flight, wings level, 30 degrees, 45 degrees angle of bank the IAS will follow.

[APenNameAndThatA]

On 29/8/2022 at 9:22 PM, Roundsounds said:

IAS means very little as you load up in a turn.
You need to be able to establish a known attitude to establish the glide. Given power + attitude = performance you only need to know the correct attitude given there’s no power. 

Power + attitude = performance isn’t actually true. Power + attitude + time + equilibrium = performance would be more accurate. 

 

If you are taking off and the engine stops, and you adopt the site picture for a Vy 45 degree banked turn, you could easily stall and spin. That is because there is every chance you will be going way less than Vy! 

[APenNameAndThatA]

3 minutes ago, Roundsounds said:

You do realise there’s quite a lag in the indications associated with the pitot / static system fitted to light airplanes? This leads to people wasting valuable time chasing IAS and I believe leads to LOCi accidents. If you practice learning and  establishing glide attitudes for various types of flight, wings level, 30 degrees, 45 degrees angle of bank the IAS will follow.

That’s a bit of a straw man, but I’m sure an accidental one. When I drop the nose, and bank as the speed climbs, there is no time to chase an IAS. 

 

The other thing is, if I drop my nose below the horizon to get to a safe speed, can you explain when I’m going to get this site picture? You can’t because I went from nose up to nose down and flew straight through it. 

 

I agree that chasing an IAS is dangerous. I think that it is far safer to lower the nose lower than the horizon. If you do that, you get safe airspeed fast, without chasing it. 

[APenNameAndThatA]

As for the lag in airspeed indication, I had not thought of that. What is it? 

[Roundsounds]

13 minutes ago, APenNameAndThatA said:

As for the lag in airspeed indication, I had not thought of that. What is it? 

It depends on the airplane type. I first saw the reality of this in a Tiger Moth fitted with a vane style ASI on an interplane strut. This ASI has zero lag, starting at around 60KIAS on climb, close the throttle the ASI was still happily indicating 55, the vane just over 40.

I won’t argue with you on the attitude, but I’ve used it in anger and am here to tell the story.

Edited August 31, 2022 by Roundsounds

[Blueadventures]

On 30/08/2022 at 9:31 AM, aro said:

 

How long does it take to descend 200'? At altitude and without additional lift, how far can you turn in 200'?

 

The equivalent altitude in powered aircraft might be 800-1000' as a guess?

Consider areo tow and the 65kts air speed the glider may have turned away from the runway centre line at 100 or 150 feet and the 65 knots allows for a tight turn.  Need more info as an IS28 would drop close to 200 feet in a turn at about 50 kts.  There was an IS28 fatal crash at Charters Towers years ago a mate witnessed the event and at times still refers to the circumstances.  

[Thruster88]

Having observed many ASI being tested in the hangar I don't believe there is any lag. It would happen if there is a significant but not complete blockage in the pitot line.

 

The reason there is no lag is because there is no flow, it is pressure in a closed system. Squeeze the hand pump on the test rig connected to the pitot tube and the needle will immediately jump up 10-20 knots and stay there if no leakage.  

 

Lag could also be caused by problems with the mechanism as facthunter said. This is why we test them in the hangar.  

Edited August 31, 2022 by Thruster88

[facthunter]

The lag is usually caused by hysteresis. Mechanisms with  fine movements have a stickiness Initial movement friction to overcome. That's the best I can explain it. In an IVSI the instrument itself has a vibrating motor inside to help overcome it. Apply a large pressure change and it's not likely to be noticed as you are dealing with a larger input.

 Re this power attitude configuration thing, I got a stick shaker at about 250 feet on final in a DC-9. All the instrument s showed ok and the Power attitude and gear/ flaps were normal also. My biggest problem was convincing the F/O as well as keeping on  and landing it.  False warnings are not nice.  Nev 

Edited August 31, 2022 by facthunter

[Blueadventures]

5 minutes ago, Thruster88 said:

Having observed many ASI being tested in the hangar I don't believe there is any lag. It would happen if there is a significant but not complete blockage in the pitot line.

 

The reason there is no lag is because there is no flow, it is pressure in a closed system. Squeeze the hand pump on the test rig connected to the pitot tube and the needle will immediately jump up 10-20 knots and stay there if no leakage.  

 

 

In gliding turning downwind to base to final the airspeed would drop a bit and students would put the nose down 'chasing the ASI number they wanted' instead of maintaining the attitude picture through the canopy.  Resulting in being over the desired / intended speed.  Only a couple of knots and there were a few seconds lag for the asi to catchup.  Apology if poor explaination.  Cheers.

[APenNameAndThatA]

15 minutes ago, Blueadventures said:

In gliding turning downwind to base to final the airspeed would drop a bit and students would put the nose down 'chasing the ASI number they wanted' instead of maintaining the attitude picture through the canopy.  Resulting in being over the desired / intended speed.  Only a couple of knots and there were a few seconds lag for the asi to catchup.  Apology if poor explaination.  Cheers.

Was the lag because the ASI took time to catch up ot because the airplane took time to accelerate. My guess is the latter, but I wasn’t there. 

[APenNameAndThatA]

Power + attitude - hysteresis = performance. Who knew?