Basic flying facts you feel you should know...

Sam D

Sam D

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Sam D
Here's something that, in 600+ hours of flying, I should probably know but don't. When a piston engine is starting, what exactly is making the sound while the engine is cranking prior to start?
 
MAKG1 said:
No. It's air movement in (and out of) the cylinders.

If you ever crank an engine with the spark plugs out, you'll notice a very different sound (hardly any at all).
Click to expand...
There is more than one sound being produced when you start an engine...
 
MAKG1 said:
No. It's air movement in (and out of) the cylinders.

If you ever crank an engine with the spark plugs out, you'll notice a very different sound (hardly any at all).
Click to expand...
With the plugs out, the load on the starter is less and you crank faster with less load on the starter.
 
On some it is the mags clicking. Impulse coupling.
 
Clacking noise? Impulse coupling. Definitely noticeable if it takes a number of blades such as during a hot start. Beat me to it. ^
 
MAKG1 said:
No. It's air movement in (and out of) the cylinders.

If you ever crank an engine with the spark plugs out, you'll notice a very different sound (hardly any at all).
Click to expand...

Really? It sounds somewhat metallic to me.
 
Walboy said:
Decent flying fact unrelated to engine facts:


Various published speeds (Vs, Vso, Va etc.) are at max gross weight

When flying at much reduced weight, like a lot of us do, the speeds can be adjusted:

Vnew = Vold * sqrt( flying weight/max gross weight )

Example:

An airplane loaded at 1950 with max gross weight of 2450 and stall speed of 60 kts

Vnew = 60kts * sqrt(1950lbs/2450lbs) = 53.5kts (roughly 10% reduction)
Click to expand...

This is a good one. I've got some real blind spots concerning aerodynamics -- like the discussion here the other day about weight, best glide and touchdown point.
 
Capt. Geoffrey Thorpe said:
With the plugs out, the load on the starter is less and you crank faster with less load on the starter.
Click to expand...

The current draw is about the same, which indicates similar motor loads.

On a 4 cylinder, compression "load" is balanced by the next cylinder. For instance, when #1 is on the compression stroke, #3 is on the power stroke (for the usual 1 3 4 2 firing order).
 
I hear the starter modulating faster/slower as each cylinder comes to TDC and changes the load on the motor.
 
Walboy said:
Decent flying fact unrelated to engine facts:


Various published speeds (Vs, Vso, Va etc.) are at max gross weight

When flying at much reduced weight, like a lot of us do, the speeds can be adjusted:

Vnew = Vold * sqrt( flying weight/max gross weight )

Example:

An airplane loaded at 1950 with max gross weight of 2450 and stall speed of 60 kts

Vnew = 60kts * sqrt(1950lbs/2450lbs) = 53.5kts (roughly 10% reduction)
Click to expand...

This is excellent. Not all speeds work that way, but the stall speed does, and anything attached to the stall speed like maneuvering speed and approach speed will as well. Not generally any of the maximum speeds, though. Most of those don't change with weight.

FWIW, I find it easier to memorize percent changes. Halve the weight reduction to get stall speed reduction. A 20% reduction in weight from max gross yields a 10% reduction in stall speed (that's your example).
 
It's the sound of my wobble pump. Trust me! That's all it is ... just the wobble pump. Nothing else ...
 
Corpsmaide said:
What's a yoke.

And...what's lift
Click to expand...

Equally important, what's yolk? and where do the chalks go?

And everyone nos theat lift is the opposite of drag...or is that gravity? no, levity is the opposite of gravity....this is all very confusing...
 
Walboy said:
Decent flying fact unrelated to engine facts:


Various published speeds (Vs, Vso, Va etc.) are at max gross weight

When flying at much reduced weight, like a lot of us do, the speeds can be adjusted:

Vnew = Vold * sqrt( flying weight/max gross weight )

Example:

An airplane loaded at 1950 with max gross weight of 2450 and stall speed of 60 kts

Vnew = 60kts * sqrt(1950lbs/2450lbs) = 53.5kts (roughly 10% reduction)
Click to expand...

Of very important note to this - Uses calibrated speed.

So per your example 60kts CAS = Vnew of 53.5 CAS, then convert to IAS as needed.
 
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