Engine failure - glide tests

[Guest]

5 hours ago, ArtVandelay said:

I’d expect more air in the cylinders means more compression resistance, hence a slower turning prop? Maybe slightly better glide.

I was thinking suction, but I agree that more air means more compression.  We’ll have to wait for @Will.iam to report back.

[ZuluZulu]

On 8/22/2022 at 12:14 AM, Skyland said:

Following up on my recent dual mag failure that resulted in an off-field landing just shy of an airport in my M20J. Luck was with me that day to find a smooth field and no damage to the plane. If only there was a way I could have extended the glide to make it just a bit further to the runway. Turns out there is a way but it seems to be a secret. To my knowledge I’ve never received training for it and don’t recall ever seeing it mentioned in a POH.

Simply pulling the prop control back to course pitch on a windmilling propeller extends the glide a considerable amount. I set about collecting some data today.

Flight test in calm air and light winds. Starting at 7000MSL, idle cut-off, windmilling propeller, 90 KIAS, 10nm glide.

First test, prop control full forward in flat pitch. Descent rate of 750fpm, over the airport at 1500MSL. That’s 550ft/nm.

Second test, same starting location and parameters except prop control pulled full back to course pitch. Descent rate of 600fpm, over the airport at 2600MSL. That’s 440ft/nm.

If my math is correct, that’s a 25 percent better glide. Wish I learned this previously but if there’s ever another engine out pulling the prop should be an automatic reach.

Fly safe.

Great work putting some real numbers on this.  But I have to point out, Don Kaye's website has been giving this advice for a while!

"We do power off stalls to the commercial standard, power on at 65% power.  By this time I have positioned us reasonably close to an airport, pull the power and tell the student we lost an engine.  They are to tell me what they are going to do. Most screw up the discussion.  I go over my "modern" emergency procedure with them using Aviate, Navigate, Communicate in that order as the mantra. During the descent I show them what happens if the prop is pulled fully back, i.e. you pick up about 300 ft/min less descent.  Then I tell them the POH says "prop full forward" and we shake our heads in disbelief."

[A64Pilot]

10 hours ago, M20Doc said:

I wonder what the effect of opening the throttle fully would have on glide performance with the engine shut down?  

It will decrease glide distance, the engine being driven is essentially an air compressor, more air you let in the greater the drag.

Engines that shut down cylinders to achieve greater fuel efficiency, shut down the exhaust valve, then the air in the cylinder is essentially a spring, takes energy to compress it, but you get most back on the downstroke. Called cylinder deactivation if you want to look it up.

A compression release is another example, “Jake brakes” are used to slow trucks down so they don’t get any energy back on what is normally the power stroke of a four stroke motor.

 

Unless you can decouple a prop from the engine, a windmilling prop will be more drag, because it’s spinning the motor. A sailboat though for example will sail faster in neutral with the prop turning than it will in gear, prop stopped. Your not windmilling a diesel with a sailboat

[Steve0715]

48 minutes ago, A64Pilot said:

A sailboat though for example will sail faster in neutral with the prop turning than it will in gear, prop stopped. Your not windmilling a diesel with a sailboat

Huh..that’s not correct.  As a long time owner of fast sailboats, we always locked the props….

[A64Pilot]

Just now, Steve0715 said:

Huh..that’s not correct.  As a long time owner of fast sailboats, we always locked the props….

Some do, most are disallowed from it as it will damage the gearbox, Yanmar’s anyway, most Yanmar transmissions have cone type clutches and locking them will over time destroy the cones, old wet plate clutch types like I had you were allowed lock the prop by putting it into reverse

https://www.yachtingmonthly.com/gear/lock-prop-let-spin-29526

‘But if you had a fast boat, you surely had either a feathering or a folding prop, surely no fast boat has a fixed prop, so it’s sort of a mute point for fast boats

Even on my Island Packet (not a fast boat) I had a Brunton’s Auto Prop, which auto adjusted pitch based on load and feathered when sailing.

My belief is that a stopped sailboat propellor has more drag due to the blades HUGE frontal area, airplane props are like sticks, where boat props are like plates.

[Steve0715]

Yes, I only had feathering props.  We locked them by reversing.  Never asked the fixed prop guys.  My last boat was an Aerodyne 43.  I had been racing since I was a teen…some 60 years past.  Owning race boats is even more expensive than airplanes.

read through the article, we’re both right!  What can’t you learn on MS?

[A64Pilot]

thread drift, but most lock sailboat props for noise reduction and wear, with a spinning prop, the whole time your sailing the stuffing box, Cutlass bearing and the transmission are all accumulating wear, stopped they aren’t.

But a sailboat prop isn’t an airplane prop, totally opposite

[Skyland]

Regarding best glides, the POH glide speed is for calm air and can be optimized for headwinds or tailwinds.  For instance, and I think everyone would agree, if at best glide speed of say 90kts while flying into a 90kt headwind there would be zero progress over the ground.  Therefore, speed up to minimize time in headwind conditions and slow down for tailwinds.  Same as normal flying if trying to optimize fuel.  How much to modify glide speed?  Suppose that's a good math problem. 

So to maximize glide, maintain book glide speed +/- for winds, prop control back, throttle at idle and lots of left rudder to keep the ball centered.

[carusoam]

4 hours ago, Skyland said:

Regarding best glides, the POH glide speed is for calm air and can be optimized for headwinds or tailwinds.  For instance, and I think everyone would agree, if at best glide speed of say 90kts while flying into a 90kt headwind there would be zero progress over the ground.  Therefore, speed up to minimize time in headwind conditions and slow down for tailwinds.  Same as normal flying if trying to optimize fuel.  How much to modify glide speed?  Suppose that's a good math problem. 

So to maximize glide, maintain book glide speed +/- for winds, prop control back, throttle at idle and lots of left rudder to keep the ball centered.

Skyland,

Good point regarding keeping the ball centered… I have rudder trim for that and can prove this an important detail….

 

I think I may be misunderstanding you….

When selecting the best glide speed…

It is based on what the ASI is telling you…

and the POH gives the details for your plane and its actual gross weight at the time….  Some Vbgs range from about 90-80ias based on GW (roughly)

 

If the air mass around you is moving….

The plane does not know it…

If you decide to change the speed that you are gliding at….

 

You have swapped the logic of what we are discussing…

Gliding at Vbg gives us the most time before contacting the ground…

Which in still air… nets us the best distance towards a safe place to land…

 

In the strong head wind case… sure…. Lower the nose to beat the headwind…

 

or get the glide rings… and pick something close that is downwind….  
 

There is probably a phrase used that describes making the best headway… when soooo many variables need to be considered….

Best regards,

-a-
 

 

[Pinecone]

12 hours ago, Steve0715 said:

Huh..that’s not correct.  As a long time owner of fast sailboats, we always locked the props….

Yeap.   Most sailboats have a prop brake.  Unless, like mine, which had a folding prop.

Folding props are found on some motor gliders.

What sailboats have you had?  We had a Laser 28.  Clocked 18.5 knots on a beam reach with the spinnaker up.

 

[Fly Boomer]

On 8/22/2022 at 10:36 PM, carusoam said:

+1 For Nate Jaros’ book on the subject… get an E-copy from Amazon for a handful of dollars… very CB friendly! And our Mooneys do better than his Brand B device…

I noticed that most of his examples were brand “B” but figured my Mooney would do better.

[A64Pilot]

As the object is to cover distance, don’t slow down any if you have a tailwind, because best glide gives you max distance

There are actually two glide speeds, max distance and min rate of descent.

In the fixed wing world glider guys would be the best to speak to the two glide speeds, I’m not a glider pilot  

Min rate of descent power off in an AH-64 was 64Kts, Max glide distance was 98 Kts, big difference.

[PT20J]

Minimum sink rate occurs at the minimum power required speed whereas maximum glide occurs at L/D max speed. Minimum sink always occurs at a lower airspeed than maximum glide speed and is often in the range of 1.1 to 1.2 Vs1.

[Steve0715]

10 hours ago, Pinecone said:

What sailboats have you had?  We had a Laser 28.  Clocked 18.5 knots on a beam reach with the spinnaker up.

 

Similar to your laser, I had a Lindenberg 28.  Then went to salt water boats with an aerodyne 38 then an Aerodyne 43. https://www.rodgermartindesign.com/portfolio/aerodyne-43-2/

sorry for hijacking a valuable discussion…

[Pinecone]

Nice looking boat.  But is it a planing hull???

Laser 28 hull was designed by Bruce Farr.  Sort of the Roy LoPresti of boats.

 

[RobertGary1]

Yea, I wouldn't found on being able to adjust the pitch of the prop after an engine failure. In my engine failure all the oil came out as the case broke up.

 

-Robert

[A64Pilot]

3 hours ago, RobertGary1 said:

Yea, I wouldn't found on being able to adjust the pitch of the prop after an engine failure. In my engine failure all the oil came out as the case broke up.

 

-Robert

However I believe most engine failures are from fuel starvation, if that’s true then pulling the prop should work most of the time.

Stick rods out of the case and likely you’ll have a stopped prop, which should be better

Either way it won’t hurt, so why not get it in your head if the engine quits and you can’t get it back to pull the prop? What could it hurt?

I question 300 FPM, but anything you get is more than you had

[David Lloyd]

Always keep in mind, when the motor quits, the airplane descends more quickly than anticipated.  Even more so when the gear is extended.

[Hank]

3 hours ago, David Lloyd said:

Always keep in mind, when the motor quits, the airplane descends more quickly than anticipated.  Even more so when the gear is extended.

This will happen immediately. The plane will pitch down immediately to maintain your airspeed at the time, at least in cruise. I'd imagine that in descent would be the same; no experience in climb configuration. 

I was testing my mags after seeing EGT rise above the redline, and the pitch down when the engine went quiet (9500 msl, WOT-/2500, 145 mphi) was dramatic enough to shock my wife. I learned about aircraft behavior and cockpit communications that day . . . .

[carusoam]

6 hours ago, A64Pilot said:

However I believe most engine failures are from fuel starvation…

 

This may be true in the general population…

MSers have been really good at not being part of the fuel starvation crowd… still some, but not most…

 

Instead we have…

broken cases dumping the oil…

broken turbos making re-start unavailable… prop still spins… unless the broken turbo dumped the oil… one turbo failure was on a Rocket…. So it’s prop feathered…  

a quick drain releasing all of the oil over the Great Lakes…
 

a vapor lock at altitude…  prop still spins, re-start was unable…

 

So many ways to dump oil overboard… or have the engine go awol….

 

When fortunate… 

Dumping drag is second nature… and pretty easy to remember…

 

When less fortunate prepare to land now…. Focus on flying the plane…

 

Now, we remember why the transition training covers these details… and some of the POHs may be missing this level of detail….

All Mooneys have about 300 pages of technical detail to be aware of…

Most Mooneys didn’t get a 300 page POH…

Some only came with a 30 page OM…

PP thoughts only, not a CFI…

Best regards,

-a-

[T. Peterson]

On 8/24/2022 at 5:54 PM, Steve0715 said:

Similar to your laser, I had a Lindenberg 28.  Then went to salt water boats with an aerodyne 38 then an Aerodyne 43. https://www.rodgermartindesign.com/portfolio/aerodyne-43-2/

sorry for hijacking a valuable discussion…

I don’t mind the hijacking. What really bugs me is that the threads all get hijacked to electric cars or sailboats - never to Goldwing motorcycles. I think I am suffering from all y’all’s micro-aggression. Calling my Psychiatrist right now!!

[Pinecone]

On 9/15/2022 at 1:04 PM, T. Peterson said:

I don’t mind the hijacking. What really bugs me is that the threads all get hijacked to electric cars or sailboats - never to Goldwing motorcycles. I think I am suffering from all y’all’s micro-aggression. Calling my Psychiatrist right now!!

Well maybe because you in wrong group of 2 wheelers.

Maybe if you talked sport bikes or cafe racers.

 

[Will.iam]

Yea i think the goldwing is more of a cessna type of bike. Nice and roomy but not as fast as the others. 
i think A Ducati motorcycle is more inline like a mooney fast hand built maybe? 

[aviatoreb]

On 8/25/2022 at 10:52 PM, carusoam said:

broken turbos making re-start unavailable… prop still spins… unless the broken turbo dumped the oil… one turbo failure was on a Rocket…. So it’s prop feathered…  

Are you referring to me?  I had a turbo-problem engine failure in flight once as you know. But I did not have a full feathering prop since I switched to the Mt4 blade - and I had a choice to get the Mt4 blade full feathering but reasons already discussed (I was worried of the failure mode of the feathering mechanism on take off - results in still power but no thrust) and also weight (it saves a good bit of weight- but the first thing was the primary reason), I did not have full feathering.  But I had lots of altitude - 16500 - and I made it to the runway maybe 15 or 20 miles away with lots of altitude to spare with commercial spirals to descend quickly.

This reminds me - in cruise on autopilot - if you loose power - don't forget to turn off the autopilot asap since if your autopilot is trying to hold altitude and you lost engine, you quickly stall.

[JackM20M]

On 8/22/2022 at 5:37 AM, Pinecone said:

I was taught this in my Commercial ASEL training.

You can feel the difference in drag.  Just set up best glide, trim, then pull the prop back.  We did it at idle power, not shutting down the engine.

So emergency procedure for engine might be prop full forward initially, but if you can't get it started, then prop full low RPM for best glide.  

And remember, if you need some drag, you can push the prop control forward again.

I was fortunate enough to learn this during my complex endorsement in my Arrow. You can really feel the difference. As mentioned, pulling the prop back won’t help without oil pressure.