General Avionics Questions

[ozrocker]

Pappy when I first saw that illustration I said to myself "WTF does the Hindenberg have to
do with prop pitch/speed/rpm on fighters,lol.
Realized it was prop blade


                                                                                <S> Oz

[hitech]

variable pitch prop as some of the WW2 A/C would have had..

Can you name any WW2 plane that had a variable pitch prop ? I have never heard of one.

HiTech

[Lusche]

.

[Ron]

I sat on the flight deck of a Sunderland once that had them.

They were adjusted by momentarily toggling switches that operated an electrical motor/actuator. (I think it was actually on the prop hub - not sure)
I guess it was mainly the domain of the Flight Engineer.

Fairey Battle rings a bell as well. I seem to remember some were only full fine, and full coarse.

I'm not sure of any others though. I'll bow to your more studied knowledge of the period.
I guess they would have only been on very early WW2 fighters due to the handling effort required., possibly the prototype spit with it's 2 blade prop..?

 

[Krusty]

A number of the lesser versions of P-40s (K or L or whatever) had electric management of the prop pitch. You pushed a switch one way or another to get finer or coarser pitch. They may have had auto pitch modes, but being electrically controlled (rather than the oil controlled type) they were unreliable.

I have also read in a couple of places that the Bf109E series had automatic pitch control, but that this did not work very well and in most cases was broken, meaning pilots did it manually.

Just as an FYI.

[colmbo]

Those electrically controlled props were probably constant speed, but the governor is controlled by an electric servo/motor.   The B-24 is set up in that fashion...good old Hamilton Standard constant speed propellors with electrically controlled governor.  There are 4 toggle switches used to adjust prop RPM.  Those prop controls are the most problematic thing on the entire airplane.  More than once we had to shutdown an engine so the flight engineer could walk out on the wing, lean over the cowling and give the prop control a sharp whack with a hammer to "unstick" it.  Another time we couldn't reduce RPM after takeoff so the co-pilot kept pushing/pulling the feather button to control prop RPM as I went around to land.  Electric prop controls are slow also....that was an issue on the P-38 IIRC -- very slow to feather.

[Ron]

They were definitely manual only.
However, It was a Sandringham (Ex Sunderland) , so it  could have had the automatics removed if they were too unreliable for a later CofA.

Pretty sure I remember the battle being variable pitch though. My Mum used to work at Faireys during the war, and I had a set of pilots notes. Still have somewhere..!

[jamdive]

Can you name any WW2 plane that had a variable pitch prop ? I have never heard of one.

HiTech

Maybe they are talking about constant speed props?

[Wmaker]

Can you name any WW2 plane that had a variable pitch prop ? I have never heard of one.

For example some Spitfire Mk.Is had them as well as Bf109Ds which were used in the Poland campaign.

[Bino]

I have read that some of the earliest examples of the Spitfire Mk. I were equipped with a three-bladed De Haviland prop that had only two positions: climb and cruise.  The following is from the recently-cited http://www.spitfireperformance.com/spit1vrs109e.html:

"...
No. 54 Squadron completely converted to "Rotol Spitfires" during December 1939. 10 The introduction of the constant speed propellers increased the Spitfire's climb rate by 730 ft/min. over that of the 2-pitch propeller equipped Spitfires
..."

[bustr]

Did/Do jet engine fan blades have the problem of the tips going supersonic during normal operation? Do they follow the same rules of interaction with air that propellers do?

[dtango]

Did/Do jet engine fan blades have the problem of the tips going supersonic during normal operation?

Yes.

Of course the curious among us will think about that for a bit and then eventually ask the question "How the heck do turbojets work when airplanes fly at supersonic speeds then???" .  To explain means entering the tricky world of compressible aerodynamics and how engine air inlets are designed for supersonic flow.  Here's an easy to understand article that starts to explain it.

Air & Space Supersonic Inlet Article

Do they follow the same rules of interaction with air that propellers do?

The interactions are quite a deal more complex than what we have with propellers.  Just flipping through a few pages on jet engine axial or centrifugal compressors in my copy of "Mechanics and Thermodynamics of Propulsion" makes my head hurt much worse than trying to understand propeller blade element theory .

[STEELE]

A big  to your Mom, Ron!  My Mother is a Nam vet (a good 5 years before I was born) 

[Ron]

Thank you Steele,

My Mum, and her sisters were pretty good at dodging bombs in the early forties.
Some of them came under more fire than the lads that went overseas.
Some heroes stay home, and change diapers...!