Primarily for general aviation discussion, but other aviation topics are also welcome.
By Ibra
#1884420
rusty eagle wrote:That's what I remember from decades ago, flying the draggy Slingsby Swallow. Penetration is vital!


I think the first time I end up "unsure of position" was on XC with K6 with 30kts winds, I was lost while termaling on local flight from an unfamiliar gliding site, no paper map & no GPS were onboard, after all it was just a quick winch & local but the sky did not stop giving

I did not want to admit or ask for help on RT, I just muddled through and found my position in Google map suing my phone, and surprise I was way downwind, the hard bit was to penetrate :lol:


One thing I try to remember for landing is that wind & gust handling depends also on wing load and drag, the generic Vref = 1.3*VS and stall speed does not fit the bill for low wing loading on gusty days, gliders are flown on final near 1.5*VS (BGA suggest 55kts for fiberglass and 50kts for wood + some gust factor), my normal approach in Turbs is 60kts which is north of 1.6*VS, in gusty days, I am north of 2.0*VS

When I fly a heavy +20lbs/ft^2 with an engine, I just nail Vref without adding anything for gusts, however, without power I will add as much speed as I can to cut through sinking & turbulent air
#1884422
Practice spot landings at an airfield where there is enough room to manoeuvre, but turn OFF the ignition after you gain confidence in your abilities with an idling engine !
#1884440
Bill McCarthy wrote:Practice spot landings at an airfield where there is enough room to manoeuvre, but turn OFF the ignition after you gain confidence in your abilities with an idling engine !


In my head, I'm trying to compose the insurance claim....

"I flipped the MAGS at 300ft, realised I was short and couldn't restart before hitting the hedge"
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By Ibra
#1884443
Sooty25 wrote:"I flipped the MAGS at 300ft, realised I was short and couldn't restart before hitting the hedge"


I would try on TMG first, AFAIK, the insurance were ok with that kind of claims :lol:

The lowest restart I had in TMG was at 200ft agl then go-around when another glider called on opposite runway, I want to be a gentleman and give the other pilot his right of way (everything set up to restart with press of button)

As always with 30 people hanging around the lunch point that day, the word went quickly to my gliding club CFI, he was not even bothered about low engine restarts nor **** or impressed, his one single comment: do whatever you wish with that engine but next time if you go-around don't go freestyle to overfly neighbor houses, just keep it on runway heading !

The checklist to restart was PMT-AM-FM, I was told PMT relates to moods of the engine his hormonal cycle :lol:
#1884460
Out of interest, EFATO etc is always taught with engine at idle, but what sort of difference in glide ratio should one expect for a windmilling prop, or entirely stopped/seized prop if conducting a forced landing for real? Negligible, or enough to notice and be surprised by it?
#1884462
flyingearly wrote:Out of interest, EFATO etc is always taught with engine at idle, but what sort of difference in glide ratio should one expect for a windmilling prop, or entirely stopped/seized prop if conducting a forced landing for real? Negligible, or enough to notice and be surprised by it?


Ah! A very sensible question which you would think would have a simple answer. There will now be pages of discussion about why a windmilling prop creates more drag than a stationary one. It does, but I've never seen a convincing and complete explanation as to why.
An idling prop does give you a bit of thrust (or reduced drag anyway) so there is a just noticeable difference with the engine off. How much depends on type I guess.
The difference is not enough to make practice with the engine at idle unrealistic.
By Ibra
#1884472
flyingearly wrote:Out of interest, EFATO etc is always taught with engine at idle, but what sort of difference in glide ratio should one expect for a windmilling prop, or entirely stopped/seized prop if conducting a forced landing for real? Negligible, or enough to notice and be surprised by it?


The difference will be along 1:10 vs 1:12 in many aircraft assuming you adjust speed (someone will soon tell us they fly forever on their type by adjusting prop pitch on dead engine), at 500ft EFATO that is 100ft
You may also want all drag to slow down before crashing in the field? so any question about prop, gear & flaps, well it depends !

On EFATO, I will not touch anything bellow 500ft agl other than pushing stick & cutting fuel and cracking door open, I have 50ms to do the first, 1s to do the rest

PS: a dead engine is likely to break and lose oil, if the hit reaches the spinner, in single engine prop will go fine pitch, on twins it goes coarse (this is regardless of what you do with blue lever), on idle & dead engine, I think I have seen different behaviours of prop in SF25, HK36, DA42 depending on speeds…I think best is to have a manual feather mechanism or just ignore it
Last edited by Ibra on Wed Nov 24, 2021 7:45 pm, edited 6 times in total.
By pullup
#1884473
flyingearly wrote:Out of interest, EFATO etc is always taught with engine at idle, but what sort of difference in glide ratio should one expect for a windmilling prop, or entirely stopped/seized prop if conducting a forced landing for real? Negligible, or enough to notice and be surprised by it?


I tried this at 1000 ft mid downwind in a Super Cub. The runway was in excess of 6000 feet long.

The extra height loss was enormous and almost immediately had to do a 180 to land.

The other important point, rarely mentioned, is the difference in trim. Once the residual power is removed there is a very noticeable nose down trim change on a Super Cub which requires a lot of handle winding whilst also being forced into an early final turn.

It could be that some aircraft run out of trimmer.

Be very careful doing these things.
By TopCat
FLYER Club Member  FLYER Club Member
#1884484
lobstaboy wrote:An idling prop does give you a bit of thrust (or reduced drag anyway) so there is a just noticeable difference with the engine off. How much depends on type I guess.
The difference is not enough to make practice with the engine at idle unrealistic.

I've posted this before - I measured my glide ratio once. The results were interesting - obviously these numbers apply only to my aeroplane:

Engine on at idle...............................9:1
Engine off, prop windmilling........8:1
Engine off, prop stopped...............10:1

So for practising short glides (engine failure over land with a decent field easily in reach) an idling engine is 12.5% better than a windmilling one.

But for a long glide, after a real engine failure, that's 25% more range if I get the prop stopped. A huge difference.

I'd need to check the calculations, but ISTR that the difference between stopped and windmilling, if it all goes quiet mid channel between Dover and Calais, in nil wind, starting at 6300', is the difference between ditching half a mile out to sea, and landing in a field a mile and a half inland.

Approaching mid channel, I'm always mentally prepared for the zoom climb to the stall.
#1884485
There is another aspect to this.
The difference you will notice depends on what the idle speed of your engine is. If set faster than it should be then you'll get quite a lot of residual thrust. That can make PFL s unrealistic.
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By Genghis the Engineer
FLYER Club Member  FLYER Club Member
#1884556
Depending upon the nature of the engine failure of-course the prop may be stopped or windmilling, a cowling may be deformed, the prop may be missing, or the engine may be running stuck on a low power setting.

Similarly the wind may be unknown and changing with height.

My thinking and teaching therefore has always been to adopt techniques allowing for corrections for uncertain flightpath and never to assume that you have any meaningful knowledge of the glide angle in advance.

G
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By MichaelP
FLYER Club Member  FLYER Club Member
#1884683
When teaching in the twin an engine is ‘failed’ to idle, and then when the student goes to select feather, power is applied enough to simulate a stopped and feathered propeller.

Control Power Drag, Identify Verify, Feather/Cause Check/Fire?

The Motor Falke crowd could ‘pitch’ in since this motor glider often has a stoppable fixed pitch propeller.