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Author Topic: XC-35  (Read 36960 times)

Sheila Shigley

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XC-35
« on: October 22, 2011, 09:42:06 AM »

The XC-35 was delivered to Wright Field, Ohio in May 1937, made its first performance flight on August 5, and was involved in an extensive flight testing program for which the Army Air Corp [sic] was awarded the Collier Trophy. The lessons learned from the XC-35 played a key role in the development of the Boeing 307 and the B-29 Superfortress which was to be the first mass produced pressurized aircraft.  (Van Patten, Robert E., Air Force Magazine Online, Vol.86, No.1 January 2003)

I find it curious that the Army Air Corps was involved in vigorous testing of a model 10 Electra--dual high-priority testing for a technology of revolutionary military and civilian significance; further, that this technology was rolled out eight weeks before AE's flight and then announced a "first performance flight" four weeks after her loss.

Is it possible that Bob Wemple (or someone) modded AE's Electra to a "10-E" not by installing Pratt & Whitney R-1340 Wasp S3H1, 600 hps, but turbocharged Pratt & Whitney XR-1340-43, 550 hps?  (Can we tell from existing data whether she used 600s or 550s?)

Would it have been worth testing the turbos on this flight without making any other mods (other than the actual ones necessary to use those specific engines instead of the S3H1s)?  I.e. no cabin pressurization, etc., simply an engines test?

« Last Edit: October 22, 2011, 10:03:40 AM by Sheila Shigley »
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Martin X. Moleski, SJ

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Re: XC-35
« Reply #1 on: October 22, 2011, 02:49:09 PM »

I find it curious that the Army Air Corps was involved in vigorous testing of a model 10 Electra--dual high-priority testing for a technology of revolutionary military and civilian significance; further, that this technology was rolled out eight weeks before AE's flight and then announced a "first performance flight" four weeks after her loss.

I don't find it at all curious.  The creation of variants is perfectly normal with aircraft design.

Quote
Is it possible that Bob Wemple (or someone) modded AE's Electra to a "10-E" not by installing Pratt & Whitney R-1340 Wasp S3H1, 600 hps, but turbocharged Pratt & Whitney XR-1340-43, 550 hps?  (Can we tell from existing data whether she used 600s or 550s?)

Anything is possible.

The documentation says that she had Wasp S3H1 engines.  Various sites give various horsepower figures, ranging from 550 to 650 HP. 

Quote
Would it have been worth testing the turbos on this flight without making any other mods (other than the actual ones necessary to use those specific engines instead of the S3H1s)?  I.e. no cabin pressurization, etc., simply an engines test?

Turbochargers were invented in 1905.  It was old technology by 1937.  Engineers would want to test under controlled conditions.  I can't imagine that they would ask AE to do engine testing for them.
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           Marty
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Sheila Shigley

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Re: XC-35
« Reply #2 on: October 22, 2011, 03:43:24 PM »

I think it wouldn't have been to test the turbos as a separate technology but rather their performance with this particular airframe.
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Gary LaPook

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Re: XC-35
« Reply #3 on: October 22, 2011, 04:33:50 PM »

The XC-35 was delivered to Wright Field, Ohio in May 1937, made its first performance flight on August 5, and was involved in an extensive flight testing program for which the Army Air Corp [sic] was awarded the Collier Trophy. The lessons learned from the XC-35 played a key role in the development of the Boeing 307 and the B-29 Superfortress which was to be the first mass produced pressurized aircraft.  (Van Patten, Robert E., Air Force Magazine Online, Vol.86, No.1 January 2003)

I find it curious that the Army Air Corps was involved in vigorous testing of a model 10 Electra--dual high-priority testing for a technology of revolutionary military and civilian significance; further, that this technology was rolled out eight weeks before AE's flight and then announced a "first performance flight" four weeks after her loss.

Is it possible that Bob Wemple (or someone) modded AE's Electra to a "10-E" not by installing Pratt & Whitney R-1340 Wasp S3H1, 600 hps, but turbocharged Pratt & Whitney XR-1340-43, 550 hps?  (Can we tell from existing data whether she used 600s or 550s?)

Would it have been worth testing the turbos on this flight without making any other mods (other than the actual ones necessary to use those specific engines instead of the S3H1s)?  I.e. no cabin pressurization, etc., simply an engines test?

-----------------------------------

Are you sure that  the R-1340-43 was turbocharged? It appears to have had the same mechanical supercharger as the other Wasps with an impeller ratio of 8:1.  See attached document of P&W engine designations.
gl
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Sheila Shigley

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Re: XC-35
« Reply #4 on: October 22, 2011, 05:48:01 PM »

Sites list the XR-1340-43s as "supercharged," "turbo-supercharged" and "turbocharged."

National Museum USAF gives:

The XC-35 was fitted with a pair of Pratt & Whitney XR-1340 radial engines. These 550-hp engines were turbo-supercharged to deliver the necessary high-altitude performance.

http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?fsID=3296

Nearly all sites list one XC-35 being built; anecdotally there is discussion of two having been built but we'll need something more than anecdotes to get to the bottom of that rumor.



A whole bunch of sweet XC-35 photos:

http://www.nationalmuseum.af.mil/factsheets/factsheet_media.asp?fsID=3296
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Sheila Shigley

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Re: XC-35
« Reply #5 on: October 22, 2011, 05:54:34 PM »

Incidentally, XC-35 lists crew of three (the third guy had to run the pressurization system and high-altitude test equipment).
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Ric Gillespie

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Re: XC-35
« Reply #6 on: October 22, 2011, 06:03:52 PM »

we'll need something more than anecdotes to get to the bottom of that rumor.
The rumor is just an anecdote. We have already gotten to the bottom of it by citing documents that show that AE's engines were not changed.
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Sheila Shigley

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Re: XC-35
« Reply #7 on: October 22, 2011, 08:41:01 PM »

Clarence "Kelly" Johnson

Johnson (1910-1990) created innovative technical concepts that significantly advanced aircraft design, performance and reliability. Johnson helped design 40 of the world's top aircraft, including the Lockheed P-38 "Lightnings;" the model 10 "Electra" used by Amelia Earhart; the XC-35, the first successful pressurized cabin plane in 1936; and the "Super Electra" used by Howard Hughes to set a record-smashing flight around the world. He also designed the U-2 and SR-71 "Blackbird" which made a non-stop flight from New York to London in 1 hour, 55 minutes.

[I'm sure this is not new to any of you, but wanted to include it in the thread for background.]
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Sheila Shigley

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Re: XC-35
« Reply #8 on: October 22, 2011, 08:57:20 PM »



Kelly Johnson working in Flight Test during Model 10 Electra testing - c. late 1930s

http://rbogash.com/kelly.html
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Ric Gillespie

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Re: XC-35
« Reply #9 on: October 22, 2011, 09:06:40 PM »

Am curious why there were rumors of a 2nd.

There weren't.  At least not until the 1970s. 
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Martin X. Moleski, SJ

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Re: XC-35
« Reply #10 on: October 22, 2011, 09:08:09 PM »

I think it wouldn't have been to test the turbos as a separate technology but rather their performance with this particular airframe.

To get that data, they fly around in the vicinity of home base, keeping track of all of the relevant variables (air pressure, temperature, humidity, prop settings, manifold pressure, air speed, elapsed time, altitude, etc.), then draw up tables to use for flight planning.  They don't send two non-engineers around the world to see how the new toys run.
LTM,

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Sheila Shigley

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Re: XC-35
« Reply #11 on: October 22, 2011, 09:22:08 PM »

They don't send two non-engineers around the world to see how the new toys run.

I wouldn't presume the flight was a ruse, but rather that the new toys were serving his XC-35 so well that Kelly might have considered the turbos an equally good or superior option for his (AE's) 10-E.  One of the 35's goals was endurance, and that attribute would certainly serve AE well, though I'm not sure how the high-altitude goal (of the 35) factors in. Most refs to the turbo aspect of the 35 mention its facilitating high-altitude flight.
« Last Edit: October 22, 2011, 09:31:03 PM by Sheila Shigley »
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Gary LaPook

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Re: XC-35
« Reply #12 on: October 22, 2011, 09:28:53 PM »

They don't send two non-engineers around the world to see how the new toys run.

I wouldn't presume the flight was a ruse, but rather that the new toys were serving his XC-35 so well that Kelly might have considered the turbos an equally good or superior option for his (AE's) 10-E.
---------------------------
In what way? Her S3H1 engines put out more power and their mechanical superchargers provided all the altitude performance they could use without pressurization or oxygen. It does appear that the plane did have turbochargers in addition to the mechanical superchargers to provide additional altitude capability and to provide bleed air for the pressurization system as this photo shows one on the outboard side of the right nacelle, its the circular object. No such turbocharger appears in any of the photos of Earhart's plane.

http://en.wikipedia.org/wiki/File:Lockheed_XC-35.jpg

gl

« Last Edit: October 22, 2011, 09:43:19 PM by Gary LaPook »
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Martin X. Moleski, SJ

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Re: XC-35
« Reply #13 on: October 22, 2011, 09:32:50 PM »

They don't send two non-engineers around the world to see how the new toys run.

I wouldn't presume the flight was a ruse, but rather the new toys might at that point have been running so well on his XC-35, that Kelly might have considered the turbos an equally good or superior option for his (AE's) 10-E.

Maybe.

Maybe not.

I can't find the purchase order or bill of sale for the Electra.  I saw it somewhere online in the last year or so.  AE paid for all of the work done on her aircraft.  KJ may have been in love with the PRATT and WHITNEY engines (purchased from PRATT and WHITNEY, not produced by Kelly Johnson or Lockheed), but I doubt that he donated two of them to AE out of the kindness of his heart.

I can't deny that KJ or Lockheed or the U.S. gummint might have done so.  It's not a self-contradictory concept (such as that of trisecting an angle using only a compass and straight edge), so it is in the real of possibility.

All of the documentary evidence suggests that the Electra was not equipped with super-secret super-powerful engines.  That you can imagine that the truth might be otherwise--and might have been covered up by all of the people involved in the installation--is not documentary evidence.
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Sheila Shigley

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Re: XC-35
« Reply #14 on: October 22, 2011, 09:33:27 PM »

Sorry Gary - I edited just as you were posting.

I'm still trying to find how the turbo factors in, although it seems to not be in question that the XC-35 used turbo (most of the info sites mention it and/or the turbo's specific benefit at high altitudes).

Is it possibly the difference between the R-1340 and XR-1340 designation?
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