P-51B Part Recovered from Alpine Glacier

This part was recovered from the crash site of a P-51B Mustang on a glacier high on Mt. Zuckerhütl, on the Austrian / Italian border. The aircraft was struck by 20mm anti-aircraft rounds while strafing trains at Freising, Germany. The pilot, my uncle, bailed out when the engine failed over the Alps, and he became a POW. I have no idea what this part is, what its function is, or where it was located on the aircraft. Details:

There is a tiny part number stamped in the metal. It's either 39640 or 396401. (I can't tell whether the 1 is a digit or a small scratch in the metal.). I tried Google searches for P-51 plus the part numbers, but that led nowhere.

Aluminum

Circular - 5-1/2-inch diameter

Three 1/4-inch holes, collinear, unthreaded, spaced about 1-7/8 inches apart.

(Due to bending in the crash, and due to camera perspective distortion, the disc appears less circular in the photo than it really is, and the three holes don't appear to be in line, but actually are.)

Most interesting, the disc is flat in the center, but starting 1 inch in from the edge, the bottom half of the disc tapers from 1/4 inch thick to 1/16 inch thick. In the photo you can clearly see this slope and the steps that it creates on the left and right sides of the disc.

Stamped in tiny print on the disc, and barely visible in the photo under the part number, is 10°. I believe this refers to the angle of that taper.

The other side of the disc also has an identical taper, but it's on the top half, not the bottom half. 10° is also stamped in tiny print on the other side - the only marking there. Apparently, that 10-degree angle is important to whatever this thing does.

So, what is this, what did it do, and how did it do it?

Thanks!

Hi,

You have a fairly rare item that deserves to be saved and identified.
This is a Throttle Butterfly from The Packard V-1650-3 Merlin engine. That engine was fitted with the Bendix-Stromberg PD 18-A1 or A2 Injection carburettor. The carb had two chokes side by side and you can see that, unless this has been further dismantled, the engine suffered a tremendous impact(s) to be smashed completely out of the carburettor.
The numbers are probably Bendix-Stromberg part or serial numbers, the 10 degree marks will refer to the specifics of the item, possibly the taper.
This part is rare and the crash seems to be well identified.
A close association to the Pilot is that the Throttle butterflies were linked directly to the operation of the throttle by him, so that makes this quite sentimental, IMO.
I attach a photo of a PD 18 carburettor from Fagen Fighters on the internet.
I hope that helps you?

Eng

What was your uncle name if I may ask? And what Unit?

I got the popcorn ready!

The details given by OP would seem to be for incident involving Lt Col John T Cravey.
My id of the crash part is correct for a P51B item as shown and described.
Hopefully, more info will be posted by OP.

Eng

If you type in P-51B and AUS (or ITA) in the appropriate boxes you get multiple POW results. (AUS or ITA - Country)

Wouldn't a P-51C also use that same part number?

Crash Date:450222
MACR#:12668
Aircraft Type p-51B-15
Serial Number: 43-24797
Aircraft Nickname:_
Aircraft Code:WZ-L
Squadron:309FS
Group:31FG
AF:15
Pilot:Cravey, John T
Pilot S/N:0-665209
Pilot Status POW - Prisoner Of War
Country:AUS - Austria
Time:1400
MACR Location:Innsbruck area

Stalag VIIa Moosburg

Engineman said:

Hi,

You have a fairly rare item that deserves to be saved and identified.
This is a Throttle Butterfly from The Packard V-1650-3 Merlin engine. That engine was fitted with the Bendix-Stromberg PD 18-A1 or A2 Injection carburettor. The carb had two chokes side by side and you can see that, unless this has been further dismantled, the engine suffered a tremendous impact(s) to be smashed completely out of the carburettor.
The numbers are probably Bendix-Stromberg part or serial numbers, the 10 degree marks will refer to the specifics of the item, possibly the taper.
This part is rare and the crash seems to be well identified.
A close association to the Pilot is that the Throttle butterflies were linked directly to the operation of the throttle by him, so that makes this quite sentimental, IMO.
I attach a photo of a PD 18 carburettor from Fagen Fighters on the internet.
I hope that helps you?

Eng

View attachment 813856

Click to expand...

Many thanks - This was enormously helpful. I have parts from the crash site preserved in a box, including also two bellcranks from the tail wheel steering mechanism, the radio antenna wire, a Colonial Radio Corporation production plate for the dynamotor that powered the radio transmitter, receiver, and controls, a fragment of the windshield, and some twisted sheet aluminum from the skin. (Photos available if anyone is interested.) I am writing a document that identifies these collected parts and explains what they are. This document will be included in the box, in the hope that this collection will be passed down to future generations of the family, along with the identifications, explanations, and the story behind them. Your message just made this document much better, and I'll get a copy to you when I finish the next revision. Do I understand correctly that the tapers on this butterfly valve are an aerodynamic feature, giving the part thinner leading and trailing edges for a smoother and faster air flow when the engine is operating at high power? Thanks again - More info coming soon in a reply I'll post to Snautzer01 shortly.

EKimbrough said:

Many thanks - This was enormously helpful. I have parts from the crash site preserved in a box, including also two bellcranks from the tail wheel steering mechanism, the radio antenna wire, a Colonial Radio Corporation production plate for the dynamotor that powered the radio transmitter, receiver, and controls, a fragment of the windshield, and some twisted sheet aluminum from the skin. (Photos available if anyone is interested.) I am writing a document that identifies these collected parts and explains what they are. This document will be included in the box, in the hope that this collection will be passed down to future generations of the family, along with the identifications, explanations, and the story behind them. Your message just made this document much better, and I'll get a copy to you when I finish the next revision. Do I understand correctly that the tapers on this butterfly valve are an aerodynamic feature, giving the part thinner leading and trailing edges for a smoother and faster air flow when the engine is operating at high power? Thanks again - More info coming soon in a reply I'll post to Snautzer01 shortly.

Click to expand...

Thanks for the reply. This Throttle Butterfly is a sort of modified aerodynamic shape to work well with the strong pressures and airflow into the engine supercharger.
That said, the parts were simplified as far as possible for mass production, but you are correct that the tapered edges are shaped to give efficient airflow and minimum
turbulence, remembering that these throttles spend most of the time only partly open and the function of these plates is to control the amount of airflow into the engine,
and so, control the amount of power the engine develops.
I am pleased that the information is useful to you.

Cheers

Eng

Snautzer01 said:

Crash Date:450222
MACR#:12668
Aircraft Type p-51B-15
Serial Number: 43-24797
Aircraft Nickname:_
Aircraft Code:WZ-L
Squadron:309FS
Group:31FG
AF:15
Pilot:Cravey, John T
Pilot S/N:0-665209
Pilot Status POW - Prisoner Of War
Country:AUS - Austria
Time:1400
MACR Location:Innsbruck area

Click to expand...

Snautzer01 - Thanks for your input. The pilot was indeed then 1st Lt. John T. Cravey (later Lt. Colonel) of Montgomery, Alabama, flying out of San Severo with the 309th Fighter Squadron, 31st Fighter Group. The mission on February 22, 1945, was planned to be a bomber escort on the opening day of Operation Clarion, but the bombers did not show up at the rendezvous, due to weather. Thus the Group's three squadrons broke up into pairs to hunt for targets of opportunity. The aircraft was damaged while strafing trains at Freising, Germany, including one 20mm round that smashed through one side cockpit window and exited the other side. The aircraft seemed to be flyable, but later, over the Alps, the engine started belching fire from the exhaust stacks and seized - there was likely a very slow coolant leak. My uncle's wife received a somewhat confused communication from the War Department saying that he was flying with the squadron near Innsbruck when hit by anti-aircraft fire, but this is incorrect - He was flying with just one other pilot, and hit at Freising, near Munich. Also, the aircraft crashed in Italy, not Austria, but only just barely. The peak of Mt. Zuckerhütl is exactly on the Austrian / Italian border, and the glacier where the aircraft crashed is on the Italian side of the mountain. The nearest town is Ridnaun / Ridanna. Innsbruck is the closest well-known city, but otherwise not an important part of the story. See also my reply to Engineman.

A shame we can't make out the serial number but it's a WZ✪L