Light plane crash, Serpentine airfield, near Perth, WA.

[kgwilson]

In the other thread https://www.recreationalflying.com/topic/37047-should-we-learn-to-glide-powered-aircraft/page/2/?tab=comments#comment-498403 I advocated (twice) turning the engine off abeam the threshold when on down wind at 1000 feet and immediately turning on to base. There were posts of this not being legal etc but my reasoning was that as an ex hang glider pilot with over 1000 forced landings without power it is the only way to determine how your aircraft will glide when you have an actual engine failure. You will easily have enough height to make the runway unless you are flying a brick. And, as I said in that thread also and now confirmed here your genuine glide performance will not be as good as it is with an idling engine.

[old man emu]

Hmmm! So my suggestion to go out and play with the gliding performance of your usual aircraft wasn't so naff after all. 

[facthunter]

I think WE are already doing this every time we practice a forced landing. One of the biggest factors is  WIND. On a slow plane especially, your descent path will be quite steep when you are gliding into a wind of any magnitude at all. Your descent RATE is constant. Your failure mode may vary, If you chuck a prop blade the  engine may be gone or hanging out of distorted cowls with heaps of extra drag.. IF you manoeuver you will be gliding at a faster speed and need more lift so more drag and faster sink rate. You may only use best glide speed for a small %of the time. Gliding into wind, you MUST increase your airspeed or you will NOT make the optimal distance. Nev

[cooperplace]

I've tried switching off the engine in the jab to see what effect it makes on glide, and it's certainly significant. NB: had instructor in the RH seat. My next thing will be to simulate -at altitude and with instructor- the impossible turn. The other thing is to go through in your mind the options for EFATO before every takeoff.

[Mike Borgelt]

Unfortunately in Australia it is difficult to "just do a couple of hours of gliding. CASA has caused sport aviation to be divided into watertight silos and to actually touch the controls of a glider you need to be a member of the GFA which is expensive.

All nonsense of course and is the result of collusion between CASA and GFA to keep the latter in business. A pity because you can also do legal spin training in gliders although I'd favour renting an hours in a Pitts S2B or Citabria etc.

 

I'd caution about much of a relationship between becoming a better pilot and doing some gliding. Gliders are MUCH easier to land on the spot than are powered aircraft. High glide angle clean (may be over 40:1) and with full divebrake may be 4:1.  Lots of room for error and actually pretty easy after a little practice.

 

cooperplace, did you switch off the engine or switch off and stop the prop?

[Mike Borgelt]

FlyBoy 1960 "My comments were about a stall spin occurrence and it is much more likely to happen with the engine stopped completely than it is with the engine at idle and possibly producing around 15 hp."

 

The effect of a little residual thrust (if indeed there is any) is to slightly increase the effective L/D of the aircraft. This has no effect of stall speed or likelihood of stall. That is controlled by the stick position. I don't know about you but I like to reference the ASI frequently to check the speed is OK particularly on takeoff, circuit and landing.

[kgwilson]

When I switch the Jab 3300 engine off at 60 knots the prop stops. It may windmill at higher speeds but I've never checked. I also check the ASI frequently on takeoff, climb out & slowing to approach speed & all the way to the threshold. Never look at it again once over the fence.

[cooperplace]

1 hour ago, Mike Borgelt said:

 Gliders are MUCH easier to land on the spot than are powered aircraft. High glide angle clean (may be over 40:1) and with full divebrake may be 4:1.  Lots of room for error and actually pretty easy after a little practice.

 

Agree. Those air brakes are fantastic.

Quote

cooperplace, did you switch off the engine or switch off and stop the prop?

I'm not sure I follow you. When you switch off the engine the prop stops, at least at the 70-80 knots I was doing.

Edited December 31, 2020 by cooperplace
typo.

[Yenn]

The statement that the rudder does not turn the aircraft in co-ordinated flight sounds suss to me.

Set yourself up in a co-ordinated turn, which will mean using rudder to centre the ball. Then change the setting of the rudder. Do you not see a change of turn rate or bank angle?  If you do then something has caused that change and the only change you made was to rudder position.

The statement that elevator causes the turn is also suss. No matter what you do to the rudder in level flight it will not cause you to turn, unless you pull it so far back that you stall and spin.

What the elevator does is control your attitude, which is not necessarily the same as Angle of attack.

Angle of attack is a great concept, but most of us have no way of working out what it is at any time, but we can check our attitude so long as we are VFR.

[Jabiru7252]

Did you mean 'elevator' in this part of your comment? "No matter what you do to the rudder in level flight it will not cause you to turn, ...." Cause, my rudder makes me turn. In a turn, especially a steep one, pulling back on the elevator will tighten the turn, but we all know that...

Edited December 31, 2020 by Jabiru7252

[Marty_d]

3 hours ago, Yenn said:

The statement that the rudder does not turn the aircraft in co-ordinated flight sounds suss to me.

Set yourself up in a co-ordinated turn, which will mean using rudder to centre the ball. Then change the setting of the rudder. Do you not see a change of turn rate or bank angle?  If you do then something has caused that change and the only change you made was to rudder position.

The statement that elevator causes the turn is also suss. No matter what you do to the rudder in level flight it will not cause you to turn, unless you pull it so far back that you stall and spin.

What the elevator does is control your attitude, which is not necessarily the same as Angle of attack.

Angle of attack is a great concept, but most of us have no way of working out what it is at any time, but we can check our attitude so long as we are VFR.

This is from RC experience, but yes the elevator is the primary turn control.  Bank with aileron and up elevator to turn.  Rudder was only ever used to balance the turn, and at least with RC (where you didn't have to worry about making passengers throw up) the rudder was often omitted completely in turns.

When you think about it, it makes sense - the aileron puts the aircraft in a different attitude laterally, ie you're now flying with one wing down, and the elevator changes the pitch of the aircraft so that pitching up in a non-level attitude will cause you to turn.  To take it to the ultimate, which was often the case in RC, a 90 degree bank angle means that elevator will turn you as it's pitching the aircraft around to the new heading.

[Jerry_Atrick]

Do we not go back to put first principles in our theory to work out what effect the controls have?

 

Application of rudder in S&L flight will cause the aircraft to rotate (yaw) around the normal (vertical) plane of the aircraft. That is the primary effect. Due to the inertia of the aircraft, it will continue in its original direction, however, one wing is presented more into the relative airflow than the other less so. This causes an increase of lift (and drag but not so much) in the into-wind wing, and less life (and drag but not so much) in the out of wind wing. The result is, at some stage later (depending on airspeed, dihedral, lateral stability, etc), the into-wind wing will rise due to the lift and the out of wind wing will drop, causing the aircraft to rotate (roll) and the vectored lift would turn the aircraft. Even if one held opposite aileron to keep the wings level, the thrust line, has vectored, so it would eventually also turn the aircraft. I did read somewhere that early aircraft only had rudders and they used to make wide, skidding turns; before ailerons were developed, some aircraft warped their wings as well.

 

The ailerons basically reverse the primary and secondary effect... the aircraft will initially roll and continue in a straight line, however, the lift vector will cause a yaw and drag the nose around. Of course, particularly at lower airspeeds, the up going wing will initially want to drag the nose in the opposite direction (adverse aileron yaw), and this is negated by the rudder.

 

The elevator primarily controls rotation around the lateral plane of the aircraft and pitches the nose up or down around the axis. In a propellor aircraft, its secondary effect is a change in airspeed. In a roll, it can intensify the rate of turn..

 

Well, that's what I recall learning in PPL theory, anyway.

 

And I know it all depends on inertia, airspeed, etc.

Edited December 31, 2020 by Jerry_Atrick

[APenNameAndThatA]

17 hours ago, Yenn said:

The statement that the rudder does not turn the aircraft in co-ordinated flight sounds suss to me.

Set yourself up in a co-ordinated turn, which will mean using rudder to centre the ball. Then change the setting of the rudder. Do you not see a change of turn rate or bank angle?  If you do then something has caused that change and the only change you made was to rudder position.

The statement that elevator causes the turn is also suss. No matter what you do to the rudder in level flight it will not cause you to turn, unless you pull it so far back that you stall and spin.

What the elevator does is control your attitude, which is not necessarily the same as Angle of attack.

Angle of attack is a great concept, but most of us have no way of working out what it is at any time, but we can check our attitude so long as we are VFR.

If you are in a coordinated turn and then change the setting of the rudder, you see a change of turn rate - but you are no longer in a coordinated turn.

 

About the elevator not turning you in level flight: that's true, but you can't do a coordinated turn if you are in level flight.

[spacesailor]

SO

Ailerons Start the co-ordenated turn, ( one wing higher ), The elevator seconds it.

THEN,

the rudder stops nauseating the passenger?.

Nothing to help turning the aircraft. LoL

Ending Uncoordinated.

Thars why I Failed my exam,s.

spacesailor

[facthunter]

Jeez, there's enough confusion there for a while.  You DO turn the plane with rudder if you are kicking it straight from a crab when landing but you must hold the into wing down or it will rise due to the further effect of the rudder induced yaw. 

 In a turn you turn primarily because you have banked the aircraft and tilted the lift force towards the direction of turn required. The greater the bank the more rapid the turn. Nev

[spacesailor]

SEE

Everything I was told in training was wrong !. LoL

spacesailor

[facthunter]

I wasn't JUST referring to your post, Spacey.. Nev

[spacesailor]

Thanks,

But it,s just another thing turned on it,s head from training.

, like rudder pedal being like soapbox trolly, ( opposite actually ),

Icing caused by moisture  ( without temprture ).

A few that made it harder to learn aviation.

Have tried since the age of fifteen, when I joined the Old AirTrainingCorpse.

Still have the same dream.

spacesailor

[facthunter]

I too had lots of soapbox trolley experience which is the complete opposite of the way the rudder works.   Nev

[FlyBoy1960]

52 minutes ago, facthunter said:

I too had lots of soapbox trolley experience which is the complete opposite of the way the rudder works.   Nev

 

Not in a Trike !

[APenNameAndThatA]

1 hour ago, spacesailor said:

SEE

Everything I was told in training was wrong !. LoL

spacesailor

We've all been there. I was told that in a stall it is okay to lower the nose and apply power at the same time. And I repeated that on this forum! (You have to lower the nose first, because adding power might pitch you up and yaw you to the left, which is not what you want to do if you are stalled close to the ground!)

[Yenn]

I give up. That is why I would never have been a good instructor.

[Jase T]

Try this. Enter a coordinated turn, the more the AOB the more you will notice it but it works at any. Now without worrying about maintaining height increase the back pressure. What happens to the rate of turn? Thats right it increases. Now reduce the back pressure. See it slows down. In fact if you reduce it enough you can stop the turn all together. The steeper the turn the more back pressure the faster the turn (until you exceed the critical angle). Ailerons and rudder do not turn the aircraft. If I put in enough aileron and keep it there I will do an aileron roll. The aircraft will not turn at all it will roll about a point. Same with rudder if i put it in and hold it I will get a sort of snap roll.. Its the back pressure that turns the aircraft (well its the increase in AoA and associated increase in lift). The others set the aircraft up so it can. 

Edited January 1, 2021 by Jase T

[Jase T]

Because there is always someone who can explain it better than i can....

 

https://youtu.be/nWbk3jn0GK4

[poteroo]

On 31/12/2020 at 8:23 AM, APenNameAndThatA said:

Maybe, the reason that people spin when they are trying to return to the airfield is not that they try to stretch the glide, but that they use the same view through windscreen as they are used to, when, in fact, they need the nose much lower than they have ever had it in the past!

 

Yes, but the reason is probably that in a maximum rate + minimum radius turn, without power, your nose attitude will need to be quite alarmingly lower than any 'normal' descending' turn in order to keep it unstalled. If you need to minimise the time taken in the manoeuvre, then you'll be flying an AoB of ( optimum is about 43o - according to experienced pilot Barry Schiff), and that requires you to keep an IAS of at least 20% higher than Vs.  Vs is of course variable according to MTOW, and also due to the amount of slipstream 'wash' flowing over the inner wing: no power & stopped prop = nil help in reducing Vs.  Schiff has done some actual in flight testing on this - google it.