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 Post subject: Experimental B-25
PostPosted: Sun Mar 20, 2011 11:14 pm 
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I was just reading about the last post on the Desert Rat and wondered if anyone in the warbird field that is involved with the North American B-25, have ever given it any thought about putting a pair of R-2800s on a Mitchell like the NA-98X. Would be interesting to see that "Experimental" example/category back in the sky.

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 Post subject: Re: Experimental B-25
PostPosted: Sun Mar 20, 2011 11:49 pm 
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I haven't heard of anyone in the civilian world considering doing this. Of course the experiences of North American and the NA-98X were obviously not very successful. It is hard to say if the wing separation was due to the stress of the additional speed, the increased stress on the wing attach points due to the enlarged aileron and increased roll rate, or perhaps a combination of things.


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 Post subject: Re: Experimental B-25
PostPosted: Mon Mar 21, 2011 4:50 am 
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The reason the "experiment" wasn't successful, is because the Air Corps pilot flew the airframe way past its structural limits. NAA prohibited their personnel from flying with him because he was flying the ship outside its structural limits. He was wringing it out. If he'd have operated the machine within the scope of design, I think there would have been a different outcome.
Hotdog the airframe with excessive G forces can only lead to the creation of new scrap for the scrapyard.

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 Post subject: Re: Experimental B-25
PostPosted: Mon Mar 21, 2011 8:17 am 
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rwdfresno wrote:
I haven't heard of anyone in the civilian world considering doing this. Of course the experiences of North American and the NA-98X were obviously not very successful. It is hard to say if the wing separation was due to the stress of the additional speed, the increased stress on the wing attach points due to the enlarged aileron and increased roll rate, or perhaps a combination of things.


This bothered me, so I went looking for my documents from NAA.
I will try to upload them in the future, I have transcribed the following for your understanding of the circumstances of the crash of the Experimental B-25 NA98X.
From my notes received directly from North American Rockwell a number of decades ago.

B-25H-NA98X #43-4406 – Pratt & Whitney R 2800 Engine

This “one only” aircraft was a test bed for the more powerful Pratt&Whitney R 2800 engine. The first flight of NA98X was flown on March 31, 1944. The NAA pilot was Joe Barton and the NAA flight engineer was Jim Talman. A person named Johnson was also aboard but his affiliation and duties are unknown. This first flight lasted one hour. There were sixteen more company test flights before the aircraft was turned over to the USAAC for evaluation.

A Major Ritchie was the Army Air Corp pilot and his flight engineer was Lt. Wey. Ritchie would fly the next thirteen test flights.

Recollections from NAA period engineers state that the Major put the more powerful aircraft through excessive flight stresses which far exceeded the operational combat requirements of an aircraft such as the B-25. He did not heed warnings to stay within red line warning boundaries.

One source claimed that Major Ritchie conducted tests that would have taxed an average fighter. A company armament engineer wanted to fly a mission or two to test the top turret modification of some sort but was advised by flight test supervision to stay out of the aircraft as long as Ritchie was at the controls.

Major Ritchie made his original, plus two additional flights, on April 22, 1944 which totaled 4:35 hours. On April 23 he totaled &:30 hours and on four of the five flights this day Sq. Leader Hartford teamed as flight engineer. On April 24 Major Ritchie, With Lt. Wey at his side, would make five flights totaling 6:40 hours.

Disaster would strike however. Returning from the 29th test flight (1:20 hours) on that 24th of April, Ritchie approached Mines Field (as it was known then and where the Inglewood plant of NAA was located) at a very high rate of speed (estimated at above red line). Evidently, structural fatigue had begun to set in on earlier flights through Ritchie’s excessive demands on the design integrity of the B25. As he made his high speed run at a runway landing approach altitude. The horizontal stabilizers were struck by disintegrating outer wing panels and gave way and the aircraft instantly came apart and crashed, killing both Ritchie and Wey. Heavier pieces, such as engines, etc., were strewn over a large area of ground adjacent to the plant and many other pieces that had flown through the air came to rest on the camouflaged screening covering the plant and the adjacent outdoor final flight line area.

The total flight test hours for NA98X totaled 40:15 hours. Total time for Major Ritchie was 18:50 hours over a period of three days. Company time totaled 21:25 hours over a period of twenty-two days including eight days of down time.

The flight time figures are from official NAA flight test records and the only comment on the flights made by Major Ritchie are simply recorded as “Army Air Corp Tests”.


References: Spivak, Holton, Ferren, and others.

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 Post subject: Re: Experimental B-25
PostPosted: Mon Mar 21, 2011 10:00 am 
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Gary, my statement isn't meant as a jab at your question. Could it have been the modifications that enabled him to put additional stresses on the aircraft? I'm not an engineer, but it seems plausible.


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 Post subject: Re: Experimental B-25
PostPosted: Mon Mar 21, 2011 11:09 am 
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Not taken as a jab, so we're cool. I don't think anything was wrong with the engineering on the airframe, I think that it was irresponsible of the PIC to fail to adhere to established procedures and recommendations of NAA and exceed the limitations of the airframe. Operator headspace killed the crew as well as the plane. Possibly too much temptation to haul a-double-s in a hopped up B-25 which is like 2 fighters tied together would not fair well in the Corp.

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 Post subject: Re: Experimental B-25
PostPosted: Mon Mar 21, 2011 11:47 am 
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Your note from Rockwell is a pretty interesting insight into the incident which you don't often see much published about.


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 Post subject: Re: Experimental B-25
PostPosted: Mon Mar 21, 2011 12:33 pm 
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can you imagine the valuable data that could have been gained if the PIC of the AAC fight tests, would have followed the procedures prescribed by North American? would every J model been equipped with the Pratt? I imagine that the overall advantage would have been a significant increase in climb rate and cruise speed. Is the Wright better than the Pratt for the B-25? I am by no means a powerplant expert, I just know both sound wonderful to me.

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