Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: earl1937 on September 23, 2013, 01:25:27 PM
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:airplane: One of the great aircraft during the "prop" age was the North American F-82 "Twin-Mustang", designed and developed during WW2, but for the want of engines, never actually saw service during the big war. The production line didn't start running until 1946, with the U.S. seeing the "cold" war coming, needed a long range fighter to escort B-29's and B-36's over vast distances to and from the target areas.
In the postwar era, Strategic Air Command used the planes as a long-range escort fighter. Radar-equipped F-82s were used extensively by the Air Defense Command as replacements for the Northrop P-61 Black Widow as all-weather day/night interceptors. During the Korean War, Japan-based F-82s were among the first USAF aircraft to operate over Korea. The first three North Korean aircraft destroyed by U.S. forces were shot down by F-82s, the first being a North-Korean Yak-11 downed over Gimpo Airfield by the USAF 68th Fighter Squadron.
On 27 February 1947, P-82B 44-65168, named Betty Jo and flown by Colonel Robert E. Thacker, made history when it flew nonstop from Hawaii to New York without refueling, a distance of 5,051 mi (8,129 km) in 14 hr 32 min. It averaged 347.5 miles per hour (559.2 km/h). This flight tested the P-82's range. The aircraft carried a full internal fuel tank of 576 US gallons (2,180 l; 480 imp gal), augmented by four 310 US gal (1,173 l; 258 imp gal) tanks for a total of 1,816 US gal (6,874 l; 1,512 imp gal). Also, Colonel Thacker forgot to drop three of his external tanks when their fuel was expended, landing with them in New York.
(http://i1346.photobucket.com/albums/p684/earl1937/F-82B_Twin_Mustang_44-65168_Betty_Jo_taking_off_from_Hickam_Field_1947_zps15a01f08.jpg) "Betty Jo" taking off on historic flight to New York", (Note C-47, B-25 and C-54 in background).
During World War II, the P-51 Mustang had escorted Boeing B-17 Flying Fortress and Consolidated B-24 Liberator bombers from bases in England and Southern Italy to targets throughout Nazi-occupied Europe. However, the Cold War brought on the challenge of possible B-29, Boeing B-50 or Convair B-36 bomber missions into the Soviet Union. The sheer size of the Soviet Union dictated that a bombing mission would be a 12-hour affair there and back from bases in Europe or Alaska, most of it over Soviet territory. Also the weather, which was bad enough in Western Europe, would make bombing missions impossible over the Soviet Union between October and May. With no long-range jet fighters yet available to perform escort missions for the strategic bomber force, the mission of the 27th FEW was to fly these long-range missions with their F-82Es.
(http://i1346.photobucket.com/albums/p684/earl1937/734px-F-82g-339thfs-1950radarequiped_zpse4889308.jpg) A flight of F-82E's, radar equipped.
The F-82E had a range of over 1,400 mi (2,300 km), which meant that with external fuel tanks it could fly from London to Moscow, loiter for 30 minutes over the target, and return, the only American fighter which could do so. It also had an operational ceiling of 40,000 feet (12,200 m), where it could stay close to the bombers it was designed to protect. The first production F-82Es reached the 27th in early 1948, and almost immediately the group was deployed to McChord AFB, Washington, in June, where its squadrons stood on alert on a secondary air defense mission due to heightened tensions over the Berlin Airlift. It was also believed that the 27th would launch an escort mission, presumably to the Soviet Union, if conflict broke out in Europe. From McChord, the group flew its Twin Mustangs on weather reconnaissance missions over the northwest Pacific, but problems were encountered with their fuel tanks. Decommissioned F-61 Black Widow external tanks were found at Hamilton AFB, California, which could be modified for the F-82; fitted on the pylons of the Twin Mustang, these solved the problem. With a reduction in tension, the 27th returned to its home base in Nebraska during September, where the unit settled down to transition flying with their aircraft.
The Twin Mustang had a very short operational life. About two years after its introduction to SAC, the F-82E was phased out of service in favor of the jet-powered F-84 Thunderjet for bomber escort duties beginning in 1950. Some were sent to Korea for combat, others were sent to Alaska, but most were declared surplus and were being sent to storage and ultimately reclamation in 1951. Air Defense Command's F-82Fs began to be replaced by F-94 Starfires in 1950, and by early 1951, with most being sent to the smelters, although a few Twin Mustangs remaining in ADC towing aerial targets. In the Pacific, the F-82Gs in combat were also replaced by the F-94 in late 1951 and early 1952, with the survivors being sent to Alaska after being modified to the F-82H configuration in Japan for cold-weather use.
With a max speed of the "G" of 482MPH and a range of 2350 miles, it was truly a great "fill in" aircraft. It carried 6, M2 machine guns and could carry 25, 5 inch rockets or 4,000 lbs of bombs.
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Must have been weird to handle with the pilot off-center like that?
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Must have been weird to handle with the pilot off-center like that?
:airplane: Not really, the main gear was spread wide enough that it was actually easier to land in a x-wind than the regular 51K! The reason I called it "Double Trouble" is with 2 engines, of course, you have 2 maintenance problems instead of one!
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what about maneuvers inflight? Anything a pilot would have to remind himself of or do differently because he is offset quite a bit from the center? And how were the guns converged?
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The have very little in common with the Mustang. Very neat aircraft though.
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The have very little in common with the Mustang. Very neat aircraft though.
Fuselages, vertical stabilizer, wings, engines, landing gear, canopies, props.......?
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Fuselages, vertical stabilizer, wings, engines, landing gear, canopies, props.......?
:airplane: Actually, they took 2 "H" model fuseledge and added 47 inches behind the two cockpits, added, if memory serves 11 inches in length and 4 inches in height to the dorsal fin, for better single engine handling. All 6 of the M2's were "center" wing mounted, therefore they were much more accurate and you could load the 'trees" with 25, 5 inch rockets.
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what about maneuvers inflight? Anything a pilot would have to remind himself of or do differently because he is offset quite a bit from the center? And how were the guns converged?
:airplane: You really didn't notice the "other" side, unless you looked at it. Aerobatics were good to excellent and with the addition of slightly wider flap area, would turn on a dime under 200IAS. Climb like a rocket ship and would, at 45 inches MP, hold a 365MPH IAS at level cruise at 15,000 feet. I only managed to get 6.2 hours in the E model and was advised not to spin the aircraft on purpose. Takeoff and departure stalls were a "hoot", nose straight up in the air and you had no idea which way it was going to break, but most of the time to the left. You could do loops from cruise all day long if you like, because it recovered back to cruise quickly. If you wanted to loop from say 15,000 to 19,000 feet, and back to 15,000, usually was a 3.5 G maneuver, you had to reduce power on the down side or you would quickly get to VNE of 489IAS. Rolls were a dream! 4 point rolls were sharp and precise because of the two rudders, were easier than any single engine I flew. What you had to be careful about was ground handling, as you had a much wider wingspan than the D or K models. The "follow me" jeep never wanted to drive over 10MPH and you could taxi this thing at 30MPH if you wanted to.
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Earl were they counter rotating engines like the P38?
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:airplane: Actually, they took 2 "H" model fuseledge and added 47 inches behind the two cockpits, added, if memory serves 11 inches in length and 4 inches in height to the dorsal fin, for better single engine handling. All 6 of the M2's were "center" wing mounted, therefore they were much more accurate and you could load the 'trees" with 25, 5 inch rockets.
Incorrect. This is an entirely new aircraft, and not just an extended P-51 with two fuselages.
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Incorrect. This is an entirely new aircraft, and not just an extended P-51 with two fuselages.
No, it is correct. When Wiki says "it was an entirely new design", it is referring to the P-51H, which is a new design over previous P-51 models (in that the airframe, propulsion, and subsystems were redesigned, according to America's Hundred Thousand, by Dean). The F-82 was two P-51H's put together, but then of course there were a lot of design mods and tweaks to do to make that work. I don't think that the F-82 was a new design from scratch.
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I think that it's very cool that Earl flew one. That must have been great fun! <S>
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:airplane: Actually, they took 2 "H" model fuseledge and added 47 inches behind the two cockpits, added, if memory serves 11 inches in length and 4 inches in height to the dorsal fin, for better single engine handling. All 6 of the M2's were "center" wing mounted, therefore they were much more accurate and you could load the 'trees" with 25, 5 inch rockets.
Earl,
The basis for the design is a lengthened H fuselage, but the reality of building a different aircraft with new points of fatigue necessitated that they redesign the entirety of the fuselage. I was heavily involved in the former CAF P-82 acquisition and restoration before the Air Force stole the aircraft and took it to Dayton. The differences are one of the major reasons that these aircraft are so rare. Almost nothing that goes on a Mustang fits on a Twin Mustang short of GFE and cockpit items.
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Fuselages, vertical stabilizer, wings, engines, landing gear, canopies, props.......?
Every one of those items is different.
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Yep, Brooke is basically correct.
Splitting hairs, Twin Mustang was developed using two XF-51F (the light weight experimental P-51 which became the P-51H production aircraft) fuselages which were lengthened by 57" for additional fuel tanks/other equipment, same goes for the outer wing panels.
As for the guns, the first XP-82 had M2 guns but second prototype already had M3s and thus all the production aircraft were armed with M3s as well.
Source: Squadron Signal's Twin Mustang book
:airplane: You really didn't notice the "other" side, unless you looked at it. Aerobatics were good to excellent and with the addition of slightly wider flap area, would turn on a dime under 200IAS. Climb like a rocket ship and would, at 45 inches MP, hold a 365MPH IAS at level cruise at 15,000 feet. I only managed to get 6.2 hours in the E model and was advised not to spin the aircraft on purpose. Takeoff and departure stalls were a "hoot", nose straight up in the air and you had no idea which way it was going to break, but most of the time to the left. You could do loops from cruise all day long if you like, because it recovered back to cruise quickly. If you wanted to loop from say 15,000 to 19,000 feet, and back to 15,000, usually was a 3.5 G maneuver, you had to reduce power on the down side or you would quickly get to VNE of 489IAS. Rolls were a dream! 4 point rolls were sharp and precise because of the two rudders, were easier than any single engine I flew. What you had to be careful about was ground handling, as you had a much wider wingspan than the D or K models. The "follow me" jeep never wanted to drive over 10MPH and you could taxi this thing at 30MPH if you wanted to.
Very very cool Earl! Thank you so much for sharing your experience. Twin Mustang was one of those aircraft that I was really fascinated with when I learned about its existence when I was 10 years or so old. :) It really left an impression on my mind at the time. :)
I'm really interested in hearing how did you get to fly it. Ie. how were those flights related to your service/training at the time?
Nice cut-away:
(http://sfw.so/uploads/posts/2013-01/1357872589_wr55209.jpg)
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Earl were they counter rotating engines like the P38?
:airplane: The early tests in the F-82, it would not get off the ground! They had arranged the counter rotating props where the ascending blades on both engines arrived at the same time, in parall to the center section. I don't know the in and outs of the problem, other than what I discovered researching that question for you: The XP-82 was to be powered by two Packard-built Rolls-Royce V-1650 Merlin engines. Initially, the left engine was a V-1650-23 with a gear reduction box to allow the left propeller to turn opposite to the right propeller, which was driven by the more conventional V-1650-25. In this arrangement both propellers would turn upward as they approached the center wing, which in theory would have allowed better single-engine control. This proved not to be the case when the aircraft refused to become airborne during its first flight attempt. After a month of work North American engineers finally discovered that rotating the propellers to meet in the center on their upward turn created sufficient drag to cancel out all lift from the center wing section, one quarter of the aircraft's total wing surface area. The engines and propellers were then exchanged, with their rotation meeting on the downward turn, and the problem was fully solved. The first XP-82 prototype (44-83886) was completed on 25 May 1945, and made the type's first successful flight on 26 June 1945. This aircraft was accepted by the Army Air Forces on 30 August 1945, whose officials were so impressed by the aircraft, while still in development, that they ordered the first production P-82Bs in March 1945, fully three months before its first flight.
Prototype XP-82s, P-82Bs and P-82Es retained both fully equipped cockpits so that pilots could fly the aircraft from either position, alternating control on long flights, while later night fighter versions kept the cockpit on the left side only, placing the radar operator in the right position.
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Earl,
The basis for the design is a lengthened H fuselage, but the reality of building a different aircraft with new points of fatigue necessitated that they redesign the entirety of the fuselage. I was heavily involved in the former CAF P-82 acquisition and restoration before the Air Force stole the aircraft and took it to Dayton. The differences are one of the major reasons that these aircraft are so rare. Almost nothing that goes on a Mustang fits on a Twin Mustang short of GFE and cockpit items.
:airplane: My memory is getting bad! Just discovered that it was in fact, a 57 inch "Plug" which they placed behind the cockpits, not 47 inches as I had thought. Gosh, time flies and memory fades. Did they recover the F-82 that you were working on from Davis-Monthan? The last time I had a chance to visit that sad place, there were, as I remember 5 or 6 in different conditions, or it might have been just several different parts that I was looking at.(In 1966)
Don't mean to sound melodramatic, but wouldn't you like to have the money and resources to just go though that place and say: "Rebuilt this one, that one". (Talking about all the different aircraft left there).
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Earl,
The basis for the design is a lengthened H fuselage, but the reality of building a different aircraft with new points of fatigue necessitated that they redesign the entirety of the fuselage. I was heavily involved in the former CAF P-82 acquisition and restoration before the Air Force stole the aircraft and took it to Dayton. The differences are one of the major reasons that these aircraft are so rare. Almost nothing that goes on a Mustang fits on a Twin Mustang short of GFE and cockpit items.
:airplane: Not sure where you got your info, but: ailerons, flaps, rudders, main landing gear and tail wheel, engines and props were the same as the H. As I understood it, when they "stretched" the fuseledge, they added additional stringers and gussets to strenghen the added 57 inches to fuseledge. The tooling jigs for all those items where already in place, why would they spend research money, when they had something which could be modified to use on the new F-82? The outer wing panels were straight off the P-51H assembley line, the only exception and new development was the center wing section, which had to have the main wing spar designed and produced.
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In this arrangement both propellers would turn upward as they approached the center wing, which in theory would have allowed better single-engine control.
And that doesn't make any sense. If I understand this correctly the right engine would be clockwise, the left engine counter-clockwise. This puts the descending (higher thrust) blade to the outside which degrades single-engine performance by creating more yaw. (This is the way the P-38 was configured however)
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(http://i836.photobucket.com/albums/zz281/Megalodon2/p-82-1_zps88499bb0.png)
The wings had the guns and landing gear recesses removed
:cheers:
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And that doesn't make any sense. If I understand this correctly the right engine would be clockwise, the left engine counter-clockwise. This puts the descending (higher thrust) blade to the outside which degrades single-engine performance by creating more yaw. (This is the way the P-38 was configured however)
:airplane: Yep, made no sense to me either! With the acending blade on the outside, though, because of the off centered thrust, the "P" factor and torque was a problem in single engine operations, but you had 2 rudders instead of one to over come those two problems.
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Can you imagine the "Oh crap! feeling they figured that one out. Thanks Earl.
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Mr. Earl,
We acquired "our" P-82 from the CAF in the early 2000 years. It was an aircraft they had been given by the Air Force in free and clear title back in the 60's or 70's. They operated it all they way up until the '80's or '90's when a hard landing forced them to put her up. The lack of available spares and prevailing costs to fix such a unique aircraft were part of the reason it never flew again. We had intended it to be fully restored but were having a hard time finding a counter rotating prop and were in the process of having a few made when the Air Force decided they wanted it. So, they used their powers and the US Government to take it back even though the title had been legally transferred. In the end, it turned into a very costly mess.
Sadly, there is very little if anything left at Davis-Monthan from that era that the smelters did not get. To have had that money in the '60's and '70's would have been a dream....
As for the info I have, all of it was gleaned from being involved in the project and the research it took to allow restoration to begin. Could I be wrong, sure, so I apologize if something is in error as it has been several years since we dealt with the P-82.
Basically, the specifics that I remember were that the wings are redesigns because of the placement of the gear changes the structure significantly. It is not a simple skin over as the gear wells have large castings and formers that are heavy. They did not leave them in place as it would not be a tremendous waste in weight. As I am sure you are well aware, the gear well on a single engine Mustang is a very weak structural link when it opens and actually requires a mechanical up lock on the door to prevent the door from creeping down in flight and thus being ripped off causing subsequent structural failure of the wing. This area changed significantly from an H series Mustang. The "plug" in the fuselage in the XP-82 changed from just an add on to actually widening and changing fuselage formers. The doghouse radiator assemblies are different, but I do not remember if the radiators are or not, but I would lean them towards being different. The vertical fins are larger and that I believe that changed the rudders. I can not remember on the flaps or ailerons, it has been too long. I remember the canopies being different as well as I believe the forward structure for the windscreen. I also remember the landing gear being stronger to make up for the significant weight increase from the single engine mustangs.
As for changing existing assembly techniques, that's too hard to guess with the military industrial complex. They have never been good about money, but I do believe they thought there was commonality between airframes up until the XP-82 brought on the changes needed in production birds.
Anyways, that's all I have to offer to this discussion. It is amazing to hear of your experiences and stories from that era. I feel truly blessed to be able to be a part of your discussions on any subject from that era. Thank you again for your service and thank you for providing all the information that you offer up so freely.
<S>
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:airplane: Actually, they took 2 "H" model fuseledge and added 47 inches behind the two cockpits, added, if memory serves 11 inches in length and 4 inches in height to the dorsal fin, for better single engine handling. All 6 of the M2's were "center" wing mounted, therefore they were much more accurate and you could load the 'trees" with 25, 5 inch rockets.
(http://i836.photobucket.com/albums/zz281/Megalodon2/p-82-2ord2_zps7ee630ab.png)
Did they ever use the drop tanks or bombs or the eight 50 gun pak 14 50's :O?
(http://i836.photobucket.com/albums/zz281/Megalodon2/p-82-2ord1_zpsa3cca342.png)
The P/F 82E was also the return of the Allison engine and re-designation from P to F.
:cheers:
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As for whether the F-82 is substantially two P-51H's or substantially different -- I completely defer to you other guys who know a lot more about it than I do.
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Folks have talked about a couple of the factors in choosing direction of rotation for counter-rotating props on twin-engine planes.
Another one is that, if the inside blades are travelling up and outside blades travelling down, it contributes to the inboard portion of the wing stalling before the outboard portion when you stall the plane under high power. Designers prefer the outboard portion to stall last so that pilots have a better chance of maintaining roll control during the stall, which is a reason that wings generally are designed with some washout (decreased angle of incidence on the outboard portions of the wing).
In Bodie's book on the P-38, it talks (I think, but could be wrong -- it has been a while since I read it) about how the first prototypes had props with inside blades travelling down, then had some issue, and reversed it in later ones. I can't remember why.
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Folks have talked about a couple of the factors in choosing direction of rotation for counter-rotating props on twin-engine planes.
Another one is that, if the inside blades are travelling up and outside blades travelling down, it contributes to the inboard portion of the wing stalling before the outboard portion when you stall the plane under high power. Designers prefer the outboard portion to stall last so that pilots have a better chance of maintaining roll control during the stall, which is a reason that wings generally are designed with some washout (decreased angle of incidence on the outboard portions of the wing).
In Bodie's book on the P-38, it talks (I think, but could be wrong -- it has been a while since I read it) about how the first prototypes had props with inside blades travelling down, then had some issue, and reversed it in later ones. I can't remember why.
:airplane: I know that both the 82 and the 38 had "teething" problems with their counter-rotating props, the 82 wouldn't even get off the ground! It took them, from what I have read a month to figure out which way to turn the the props to stop creating so much drag that the thrust couldn't overcome the problem. The 38 would not have had as much problem because it started in a more or less level attitude because of the tricycle gear and there fore asymmetrical thrust, "P" factor and torque, would not have been as acute a problem as the 82 from a nose up attitude on takeoff roll. I never flew a 38, but sat in one, took the check list and was dumb founded by the starting sequence on getting the power plants fired up.
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The way I understand it is that the prop wash creates an airflow that cork-screws around the fuselage in the direction of the prop turning. If both prop blades turns upward in front of the center wing section they will increase the effective angle off attack of that wing in relation to the local airflow, thus stalling it. This is also why one wing stalls before the other on a single engined prop plane with power on. It will be the wing on the side where the prop turns upward. At least that's how I understand it.
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(http://brianherscher.com/BrianHerscher/Aerodynamics_files/droppedImage_8.jpg)
(http://people.bath.ac.uk/ensmjc/Research/corsair.gif)
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If both prop blades turns upward in front of the center wing section they will increase the effective angle off attack of that wing in relation to the local airflow
Yep. Hence maybe the desire for blades to travel up on the inboard (like the P-38) so that inboard stalls first (although, again, other factors might have been more important -- I need to look at Bodie's book).
On the F-82, they seem to travel down inboard, so I guess other factors were more important (like Earl was talking about)?
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Yep. Hence maybe the desire for blades to travel up on the inboard (like the P-38) so that inboard stalls first (although, again, other factors might have been more important -- I need to look at Bodie's book).
On the F-82, they seem to travel down inboard, so I guess other factors were more important (like Earl was talking about)?
:airplane: Just to add to discussion, any aircraft which is sitting in a 3 point stance, i.e., with a tail wheel, is going to be subjected to stronger "P" factor and torque effects than an aircraft which is a tricycle gear, with a nose wheel. In any aircraft which the prop turns to the right, as looking from the pilots seat, The torque and "P" factor pulls to the left, confirming the theory that the "descending" blade takes a more effective "bite" of air, than does the ascending blade. In any twin engine aircraft, with counter-rotating props, such as the F-82, the effects of "P" factor and torque are pretty much balance out, because the decending blade is same away from the center line of the aircraft. However, you must understand that just as you lift off the runway on takeoff, and you lose power in either of the two engines, now, because the thrust line is off-set, the "P" factor and torque effect is very pronounced and very dangerous.
In viewing these responses, I am reminded of a problem that Piper aircraft company had with a "Twin Comanche"! What the NTSB found was this: if the power failed on the left engine, then, because of the short fuseledge and small vertical stabilizer and small rudder, the aircraft was almost uncontrollable below 110MPH IAS, because the effect thrust was so far away from the center line of the aircraft. If the right engine quit or lost power, the effects were nowhere as pronounced because the thrust area of the descending blade of the left engine, next to the fuseledge was closer to the center line of the aircraft. They applied the same fix as the fix on the F-82, and you had VMC the same with either engine loss.
About the same time they were having problems with this great little twin, Cessna aircraft company came out with the 337, which had one engine in front, and one engine in back, therebye eliminating VMC. The only problem that had was that if you lost the rear engine at or near gross weight, it would only climb, about 250 to 300 feet per minute. If you lost the front engine, it would climb about 500 feet per minute on the rear engine.
(http://i1346.photobucket.com/albums/p684/earl1937/twincommanche_zpsf7e5a966.jpg) Business end of a Twin Comanche!
(http://i1346.photobucket.com/albums/p684/earl1937/337cessna_zpsad179033.jpg) This us the military version of the Cessna 337, which was used as a FAC aircraft in Vietnam.
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Also reference the Cessna 337. Early on there was a tendency for the rear engine to overheat during extended taxiing. Some folks would either not the rear engine until getting to the runway to prevent the overheating problem.....but they then forgot to start/restart the rear engine and attempted takeoff with just the front engine.
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Also reference the Cessna 337. Early on there was a tendency for the rear engine to overheat during extended taxiing. Some folks would either not the rear engine until getting to the runway to prevent the overheating problem.....but they then forgot to start/restart the rear engine and attempted takeoff with just the front engine.
:airplane: You sir, are correct, I have seen that before, twice, once at Charlie Brown in Atlanta, and once at Lakefront in New Oleans. Both times, I got on the radio, as other people did, and warn the guy, as we were both on tower frequencies. If you research the NTSB accident records on the 337, I bet you would find at least 3 or 4. A doctor I knew in Atlanta had a pressurized version of this aircraft and he loved it.
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Not that I should play aircraft designer here, but if instead of one air intake on top, there would have been two on the sides below the wing? Probably not as efficient drag/wing efficiency-wise, but it would have put the intakes more into the slipstream of the front engine while taxiing. Of course you would have had to redesign the air exits then as well.
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Not that I should play aircraft designer here, but if instead of one air intake on top, there would have been two on the sides below the wing? Probably not as efficient drag/wing efficiency-wise, but it would have put the intakes more into the slipstream of the front engine while taxiing. Of course you would have had to redesign the air exits then as well.
:airplane: I have heard that discussion before by some people I have respect for and you make a good point! Why Cessna decided to do it the way they did, I don't know, guess we would have to talk to the design engineer for that one. Good question though!