silly question on best glide speed?

I was just wondering if best glidespeed in say a cessna 152 will be fast
enough to
get the engine started if you encountered a battery failure or starter
failure.

shywon

wrote:

I was just wondering if best glidespeed in say a cessna 152 will be fast
enough to
get the engine started if you encountered a battery failure or starter
failure.

Stopping the prop from windmilling generally requires slowing to just above
stall speed. That's well below best glide speed. If the prop is still
windmilling, best glide will be fast enough to let you restart.

Once the prop stops, though, it takes a lot to get it going. If you slowed the
plane enough to stop the prop, you will have to accelerate to well above best
glide speed to get the prop turning again.

George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.

As George says, you really have to work at it to make a prop stop. It will
windmill at glide speed, and the magnetos will spark their little hearts out
during every revolution until the fuel-air mixture returns to the cylinders.

If you do stop the prop...on purpose, by sticking the nose way up in the
air...you will have to dive to about 120 to get it rotating again.

Bob Gardner

wrote in message
...
I was just wondering if best glidespeed in say a cessna 152 will be fast
enough to
get the engine started if you encountered a battery failure or starter
failure.

shywon

Did the stopped-prop thing in a 150 many years ago. It would not
restart even while diving at Vne. Maybe a worn-out engine with little
compression left would start at 120.

Dan

Another problem, especially with small engines, is that if you're ever going
to get carb ice, it's now, with the fire out and the engine turning. The
exhaust manifold cools really fast on a smaller engine; you're pulling air
and water through a cold carb throat, with insufficient latent heat to melt
the resulting ice; and you may not get a restart at all.

Seth

"Bob Gardner" wrote in message
...
As George says, you really have to work at it to make a prop stop. It will
windmill at glide speed, and the magnetos will spark their little hearts
out during every revolution until the fuel-air mixture returns to the
cylinders.

If you do stop the prop...on purpose, by sticking the nose way up in the
air...you will have to dive to about 120 to get it rotating again.

Bob Gardner

wrote in message
...
I was just wondering if best glidespeed in say a cessna 152 will be fast
enough to
get the engine started if you encountered a battery failure or starter
failure.

shywon

Great point. I had the engine in a 152 die on me several years ago.
There was no restarting it at all.

Emergency landing at John Wayne Airport (KSNA), and after landing on the
runway it started right up.

John.

Seth Masia wrote:

Another problem, especially with small engines, is that if you're ever going
to get carb ice, it's now, with the fire out and the engine turning. The
exhaust manifold cools really fast on a smaller engine; you're pulling air
and water through a cold carb throat, with insufficient latent heat to melt
the resulting ice; and you may not get a restart at all.

Seth

"Bob Gardner" wrote in message
...

As George says, you really have to work at it to make a prop stop. It will
windmill at glide speed, and the magnetos will spark their little hearts
out during every revolution until the fuel-air mixture returns to the
cylinders.

If you do stop the prop...on purpose, by sticking the nose way up in the
air...you will have to dive to about 120 to get it rotating again.

Bob Gardner

wrote in message
...

I was just wondering if best glidespeed in say a cessna 152 will be fast
enough to
get the engine started if you encountered a battery failure or starter
failure.

shywon

wrote in message ...
I was just wondering if best glidespeed in say a cessna 152 will be fast enough to
get the engine started if you encountered a battery failure or starter failure.

shywon


Why would the prop stop in the air with a battery or starter failure?

Thank you all for the great answers.
I didn't say the prop stopped because of battery failure or starter failure.
It could be from too rich mixture or switching to an empty fuel tank.
I know, if you do something and the engine quits, turn the switch back
immediately.
Thanks again folks

".Blueskies." wrote in message
...

wrote in message
...
I was just wondering if best glidespeed in say a cessna 152 will be fast
enough to
get the engine started if you encountered a battery failure or starter
failure.

shywon


Why would the prop stop in the air with a battery or starter failure?

Seth Masia wrote:

Another problem, especially with small engines, is that if you're ever going
to get carb ice, it's now, with the fire out and the engine turning. The
exhaust manifold cools really fast on a smaller engine; you're pulling air
and water through a cold carb throat, with insufficient latent heat to melt
the resulting ice; and you may not get a restart at all.

Depends on the reason for engine stoppage. The vast majority of the temperature
drop within a carburettor is from the evaporation of fuel. If the engine stopped
because you just ran a tank dry, that source of "coolth" disappears and the carb
starts to warm up.

George Patterson
Drink is the curse of the land. It makes you quarrel with your neighbor.
It makes you shoot at your landlord. And it makes you miss him.

There's the other point: isn't glide range extended in a 172 if the
prop isn't windmiling?