Should we learn to glide "powered" aircraft?

[old man emu]

I'm amazed at my stupidity. I get these wild ideas for thread topics, then express it in general terms.

 

On 29/11/2020 at 1:50 PM, old man emu said:

I wasn't talking about that at all, yet the discussion has drifted into that specific area of flight.

 

What I am advocating is that instead of grabbing a plane for a session of circuits and bumps, people should go out to where aerobatics are safe and spen a good bit of time just messing around with the aerodynamic performance of their aircraft at near zero engine power.

 

Now this thread is concentrating on landing techniques. That's not what I meant. Since aerobatics are prohibited in RAAus aircraft, ane a lot of other light aircraft, exploring the glide is one one that you can have a bit of harmless fun with an aircraft. Isn't that the reason for the "recreational" in Recreational Aviation?

[Student Pilot]

I am not recommending this but I have heard of people doing it.

 

Shutting the engine down in flight, stopping the prop. The glide is totally different (So they tell me) to the engine idling or "Simulated no thrust". The glide is usually longer, controls feel completely different. The prop takes a lot more stopping than what you would think. When I was training in the olden days the instructor (Ex British Army rotary and fixed wing) did air starts. He made me do a couple in 150 and 172. I have seen it done from very high up to landing, the engine was then warmed up to taxi back. I have seen it done so the aircraft rolls up to the tiedowns. 

 

[RFguy]

Brumby610. YCWR

 

--if base turn is 45deg off shoulder  to threshold (normal) , need to wait until about 1/3 way in on base  to make it on a glide.  otherwise will be short.

Engine happy  IDLE  rpm 2400 ish (rotax) . 

 

Flaps only when I know I am ASSURED of making  it. As my headwind assessment is often optimistic. 

 

-- shortened downwind  engine fail  approx abeam of the keys, can make it from downwind, land halfway down main runway.

 

-- Anything earlier than that on  downwind,  (Cowra YCWR )  I use the grass cross strip (03/21) ....

 

-- On upwind departure, >= 500 ' ,  (33/15) , after turning any excess airspeed into height, I will llikely use the cross strip (03/21) with a right steep  descending  turn . that's actually probably the best option since it is only a 240 deg swept turn.

compared to a 300 deg swept turn for the upwind cross. However, right turn , approach will be over the edge of town, a caution.

- cross provides continuous visual of landing point through the turn

-- if cross is unavailable and  more height ,  I will go back to the strip (and land downwind if not windy). cross strip if windy on the main.

prefer cross wind than strong tail wind. 

 

-- adjustment required as headwind /cross wind increases, as you'd expect.

 

-- NO LOW TURNS ,  NO glide stretching.....

Edited December 1, 2020 by RFguy

[facthunter]

A good % of significant tail wind forced landings go wrong and if you are still flying when it does, your 45 knot stall speed is cancelled out. While over 10 knots are used regularly by "heavies" they can end up with hot brakes and it's always a trickier deal.. . Only "Young" birds land downwind. They quickly learn not to. 

 As to low turns , rows of trees etc may require them and sideslips CAN go to the flare. Just make sure you are "practiced' in this sort of thing IF you are going to use it.  There's temptation to stretch glides, but it never works and it's even more noticed if a headwind exists . Slowing up makes the headwind blow you away for longer. Nev

[Yenn]

Tail winds will make your gllde flatter, by that I mean that you will fall less verticly in the same distance than you would with nil or head wind. that is not as good as it sounds because you will be going faster over the ground.

Somebody said all landings should be on glide slope, would they care to define what they meant by glide slope? Is it the 3 deg slope favoured by the heavies, from which we would have no hope of recovering from an engine failure?

[facthunter]

Yes  with the  wind or against it your RoD will be the same.  Mentioned in other posts that heavy wing loadings will give worse Glide angles as not so. Glide angle is a function of L/D ratio. Heavier you just go faster.. Example water ballast on Gliders. If you have a draggy plane  increase of speed will get away from the best L/D of the plane. "These" speeds are related to actual weights you are experiencing. IF your stall speed is increased so are the other "best" speeds except structurally determined ones. Nev

[Bosi72]

On 01/12/2020 at 9:59 AM, Student Pilot said:

Shutting the engine down in flight, stopping the prop

In case of carby icing, the procedure requires to pull the carby heat out, mixture rich, and ensure the fuel and switches are on. Propeller windmiling may restart the engine when ice melts. Therefore I don't think the prop will stop when in flight unless big issue inside engine.

 

Another story..

My o300 engine requires leaning when taxiing, so one day during the landing roll I pulled the mixture knob and engine stopped. I quickly pulled the starter lever, cranking, but nothing.. Lucky the exit was not far away and I managed to exit and clear the runway.. It took me another 30sec and fuel priming to start the engine and continue taxiing..

 

Lessons learned. Do not touch mixture knob from circuit to taxiway threshold.

 

 

[Tex]

On 01/12/2020 at 12:16 PM, Yenn said:

Somebody said all landings should be on glide slope, would they care to define what they meant by glide slope?

Be able to make the airstrip without power.

[Roundsounds]

On 28/11/2020 at 10:17 PM, Old Koreelah said:

Interesting topic, OME. There have been threads about whether an idling prop is a reliable indication of glide performance if the noise stops. My own experimental results didn’t agree with conventional wisdom; I just know that my glide rate is about 1:9 and I can get to anywhere under the wingtip- in still winter air.

 

I’ve met pilots who claim to have cut the engine and thermalled in powered aircraft. They must’ve been good, ‘cos my attempts were abysmal. I won’t be relying on any help from updraughts.

Depends on the type, I’ve done ridge soaring in a Citabria a few times. I left the engine at idle though. 

[RFguy]

per another post, engine idle can be negative thrust at best glide speed .

But I guess you wont be trying to be at best glide for soaring, just want to be beyond stall with appropriate airspeed margin for manouvering given a height above ground for any stall recovery .  I have learned to pitch it up in a thermal for low forward speed (and max benefit) as to stay in the thermal for longer.

A few hours in a glider in dual would probably be a useful vocation for me.

 

 

 

 

 

[M61A1]

On 01/12/2020 at 11:13 AM, RFguy said:

Brumby610. YCWR

 

--if base turn is 45deg off shoulder  to threshold (normal) , need to wait until about 1/3 way in on base  to make it on a glide.  otherwise will be short.

Engine happy  IDLE  rpm 2400 ish (rotax) . 

 

Flaps only when I know I am ASSURED of making  it. As my headwind assessment is often optimistic. 

 

-- shortened downwind  engine fail  approx abeam of the keys, can make it from downwind, land halfway down main runway.

 

-- Anything earlier than that on  downwind,  (Cowra YCWR )  I use the grass cross strip (03/21) ....

 

-- On upwind departure, >= 500 ' ,  (33/15) , after turning any excess airspeed into height, I will llikely use the cross strip (03/21) with a right steep  descending  turn . that's actually probably the best option since it is only a 240 deg swept turn.

compared to a 300 deg swept turn for the upwind cross. However, right turn , approach will be over the edge of town, a caution.

- cross provides continuous visual of landing point through the turn

-- if cross is unavailable and  more height ,  I will go back to the strip (and land downwind if not windy). cross strip if windy on the main.

prefer cross wind than strong tail wind. 

 

-- adjustment required as headwind /cross wind increases, as you'd expect.

 

-- NO LOW TURNS ,  NO glide stretching.....

I recommend doing some low level training, not necessarily an endorsement, but at least some experience.  Being comfortable turning low is just another tool in the box that may just save your butt.

I took someone's advice and did some LL training. I'm glad I did, Used it in my first engine out, which resulted in nil damage to anything instead of tangled in trees if I followed the no low turns advice.

[old man emu]

1 hour ago, RFguy said:

per another post, engine idle can be negative thrust at best glide speed .

In that other post, figures provided for a particular aircraft that showed that at 2000 rpm and 65 kts, the propeller was giving no thrust, not any drag.

 

Be nice to see the data and equations to see how they would apply to other aircraft.

[facthunter]

The usual reference to "glideslope" is the descent path from the final approach point to the runway for an ILS approach. Usually about 3,000 ft at ten miles. The ability to make the aerodrome with no power has no relevance so the term GLIDEslope is a bit if a misnomer. .It's the height/distance relationship you should adhere to to legally clear all obstacles below you safely  Nev

[Tex]

ILS approaches have no relevance to recreational aviation so it would be unusual to refer to glideslope (glide path, approach path, glide approach, 'final') in that fashion.

 

If you are on, or have, glide slope to your designated landing point it is correct to say so... anywhere in the pattern, not just for ILS. Semantics Nev.

[RFguy]

 

So a better term might be 'approach slope'....

What else is it called in instrument approach world ?

Edited December 20, 2020 by RFguy

[kgwilson]

For recreational aircraft and other light aircraft you should only be concerned about best glide. In gliding circles this is known as L/D or lift over drag ratio.  It is the number of units you move forward in still air to the number of units you move towards the ground due to gravity. For most recreational/light aircraft the value is somewhere between 8 and 12 to 1. High performance gliders have an L/D of 60:1. The VSI or Vario will tell you how many FPM you are going down. Your POH will list this value as speed in knots with no power. A glideslope however you define it is irrelevant as the wind direction and strength is always a factor.

 

I still maintain the best way to work out how your aircraft really glides is to turn the engine off at 1000 feet on downwind abeam the threshold and then turn immediately on to base and set the best glide value as specified in the POH. When approaching final you should be quite high but this depends a bit on whether you do tight or cross country circuits. You can then set the flap for a touchdown 1/3 of the way down the runway & S turn or sideslip if you are still high. If turning the engine off doesn't sit well with you pull the power to idle at the same place and adjust your approach as described. I have about 2000 forced landings without power, all when flying hang gliders and 99% of the time landed exactly where I planned to.

Edited December 20, 2020 by kgwilson

[facthunter]

VASIS is "Visual approach slope indicator." .. What is I would say is "erroneously"called a GLIDE slope is an instrument approach slope indicator  BOTH are set to 6 degrees I believe. Your  glide path would vary from plane to plane and depend on headwind. You also would not do a power off approach in gusty conditions unless you had no choice.. Nev

[Tex]

Agreed erroneous. L/D is not just best glide. Best L/D also changes i.e with weight, as does your glide ratio depending on many factors and more than just published polar data (lets avoid McCready theory discussions).

 

Required glide ratio or a required glide slope: Same thing, if you have it = safer. Again what relevance is ILS terminology to VFR rec aircraft? None. When I fly a glider my instruments tell me when I am above the required final glide slope and even give the cross section required GR, actual GR (avg) If you have a glide approach you are above or on the (required) glide slope. Pretty simple.

Edited December 20, 2020 by Tex

[old man emu]

Nobody seems to want to simply go out and see if they can emulate the behaviour of an unpowered aircraft i.e. a true glider, just for the sheer fun of it. 

 

Y'all want to get all serious about engine failure during straight and level flight. Lighten up!

[facthunter]

They don't make gliders with the poor performance of most U/L's. It's all over too quickly. I believe it's illegal to intentionally shut down an engine in flight unless with an instructor. We did it in the olden days to do inflight engine starts without the starter motor. Often  a fairly extreme manoeuvre requiring near vertical diving and a easy exceed VNE possibility. Nev

[Tex]

I wouldn't be so sure about that OME

Also still a few primary gliders around or being built... They don't glide so well, be a great challenge.

[M61A1]

2 hours ago, old man emu said:

Nobody seems to want to simply go out and see if they can emulate the behaviour of an unpowered aircraft i.e. a true glider, just for the sheer fun of it. 

 

Y'all want to get all serious about engine failure during straight and level flight. Lighten up!

Maybe that's because our regulators will get all serious if someone dares to mention that they turn their engine off for fun on a public forum.

You are basically asking people to incriminate themselves.

They wrote an article about the evils of turning off your engine in flight and made rules that prohibit it unless some stringent preconditions are met.

[old man emu]

That's why I suggested pulling the throttle back to idle revs. Keep the engine firing, but not doing much else.

[lee-wave]

 

13 hours ago, Tex said:

Agreed erroneous. L/D is not just best glide. Best L/D also changes i.e with weight, as does your glide ratio depending on many factors and more than just published polar data (lets avoid McCready theory discussions).

 

Required glide ratio or a required glide slope: Same thing, if you have it = safer. Again what relevance is ILS terminology to VFR rec aircraft? None. When I fly a glider my instruments tell me when I am above the required final glide slope and even give the cross section required GR, actual GR (avg) If you have a glide approach you are above or on the (required) glide slope. Pretty simple.

  

 

Lift drag ratio or L/D is the same as glide ratio......varying weights do not affect the LD of the aircraft or glider; only the speed at which best LD is achieved. On good thermal or ridge soaring days gliders are loaded with water ballast. The extra weight had the effect of raising the best L/D speed allowing for much faster inter thermal speeds. The price was a slightly slower climb performance.  If conditions weakened the water could be dumped.              

.......and should we 'learn to glide' powered aircraft ... absolutely we should with the motor switched off (the Jab motor does not take kindly prolonged idle glide approaches) and preferably with the  prop not rotating into a nice long grass or sealed runway into wind.   The Jab UL has a very good glide ratio of 13:1 at around 60 knots.  Also practice side slipping as much as you can even during normal approaches.  

 

Merry Christmas everyone from a completely lock downed, miserably wet UK....

[old man emu]

1 hour ago, lee-wave said:

Merry Christmas

everyone from a completely lockdowned, miserably humid Sydney....