In the case of the B-47 the Boeing designers combined the new swept wing technology that George Schairer had found in Germany with thin laminar wings. The thin wings were completely unnecessary and not used in the subsequent B-52 yet they complicated the design, created aeroelasticity problems and structural issues. The Valiant suffered a somewhat short design and development so that it would be ready quickly to carry Britain's nuclear weapons and probably suffered a few minor shortcomings from this. When fatigue did become a problem the Victor and Vulcan were ready.
B-36 - Why a Pusher??
- Thread starter Piper106
- Start date
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In the case of the B-47 the Boeing designers combined the new swept wing technology that George Schairer had found in Germany with thin laminar wings. The thin wings were completely unnecessary and not used in the subsequent B-52 yet they complicated the design, created aeroelasticity problems and structural issues. The Valiant suffered a somewhat short design and development so that it would be ready quickly to carry Britain's nuclear weapons and probably suffered a few minor shortcomings from this. When fatigue did become a problem the Victor and Vulcan were ready.
And taught Boeing more about large swept wing design with pylon mounted engines than anyone else in the world knew, or would know, for years to come.
AFAIK they never completely fixed the problem throughout the life of the plane. The Dog Sabre lived up to its name from beginning to end. One of my mech school instructors, a retired career fighter pilot and Sabre veteran of MiG alley, (2 tours) spent over half his career in various versions of the Sabre (including a USN/USMC exchange tour in Furies) and hated his two years in the "Dawg" as the low point in his career. Even worse than his tour in C124 Globemasters or his tour as an interceptor squadron liaison officer at SAGE. "I was always an "eyes out" fighter pilot. Never had any use for that scope dope stuff. Even that sorry excuse for a fighter plane, the F94, hauling a clueless sergeant RO around in the back seat, was better than the Dawg! At least it had a 'burner and an engine that would stay lit. Never had much use for overweight swept wing gliders and windmilling airborne relights"
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SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
As long as I'm not the one jacking this thread, I read a long time ago that the "best" version of the F-86 was a Canadair variant. Just wondering.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
The F-86 is one of the few jets that caught my fancy.
fastmongrel
1st Sergeant
That's always been my understanding. The Mk6 version with the Orenda 14 engine of 7,500 lb thrust.
There was an Australian version with an Avon, CAC-27 Avon Sabre with twin 30mm Aden guns and almost twice the thrust. 60% of the fuselage was altered to fit the shorter wider Avon.
fastmongrel
1st Sergeant
Not twice the thrust of an Orenda 14. Practically the same but definitely not twice
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Just looked up the CAC-27. Cool airplane.
We had an Avon at mech school. Hard to imagine a Sabre wrapped around that fireplug.
The pylons on the B-47 were dimensioned such that they damped rather than helped excite the resonant aeroelastic flutter frequency of the wings. That idea itself came from the forward swept wings of the Junkers Ju 287. Because of the aeroelastic problems of the forward swept wings Junkers designers used a twin spar design with strong skins to ensure high torsional rigidity. This required the engines to be suspended in pods so that the skin was not interrupted. The pods pendulous frequency was dimensioned to avoid anticipated flutter.
Joe Broady
Airman
- 99
- May 30, 2019
I may have given the impression that prohibited speed and rpm combinations were something unique to pushers. Not at all. "The possibility that flight and ground operation might take place at engine and aircraft conditions where flexural propeller vibration stress levels exceed allowable limits has resulted in operating restrictions." (1C-124A -1, C-124 flight manual). For instance, 1250 - 1850 rpm was prohibited on the ground except to quickly pass through that range. In flight there were additional restrictions that depended on weight and speed.
The B-36 flight handbook says, "These limitations are primarily based on propeller vibration limits but the vibrations may be of such nature that they can also weaken the propeller shaft. The vibratory forces are caused by power impulses imposed as each cylinder fires; by the aerodynamic disturbances created as a blade or blades pass through a region of turbulent air behind the wing or adjacent to the fuselage; and by other causes such as misfiring cylinders, malfunctioning vibration dampeners, and extended flaps."
Both the B-36 and C-124 used Curtiss 3-blade propellers.
Earlier I mentioned the B-36 propellers were parallel to the wing trailing edge, which was swept back 3 degrees.. This was a factor when you feathered a propeller. "On this airplane the engine nacelles are not parallel with the fuselage center line in the horizontal plane. The nacelles are 'toed in' at the propeller end, resulting in the propellers on one wing having a slightly different relative wind than those on the other wing. This condition may lead to propellers on engines No. 1, 2, and 3 windmilling in a direction opposite to normal operation when they are feathered."
That slow reverse windmilling will eventually damage an engine due to inadequate lubrication., so the engineer (coached by a gunner in the rear compartment) would jiggle the manual pitch switch to stop the rotation.
Finally, a bit of B-36 trivia. It's well known the plane entered service as a 6-engine bomber, and the jet pods were added later. What is not well known is that the pods were removable! "Occasionally, it may be desirable to operate the airplane without the pods installed to obtain maximum range (with a sacrifice in possible top speed)." Pod removal reduced the B-36H operating weight (crew + crew equipment + ammo + unusable fuel + other fluids fully serviced) from 181.800 to 167.600 lb, or a 14,200 lb loss. Max weights were 357,000 and 330,000 respectively. I have never seen a photo of a de-podded B-36. It must have happened rarely, if at all.
Those max weights are from the flight handbook charts, but the same charts show the B-36H can fly with an massive overload if you accept the risk. With one jet pod (or any two piston engines) inoperative, the weight necessary to bring service ceiling down to sea level is more than 550,000 lb.
Great info. Funny thing was, give a dog a different designation, tweak the internals a bit and sell it to your allies, with one of them putting it into production to boot, as NATO common equipment and voila! the F-86K becomes a standard NATO all-weather fighter!
With a redesigned intake duct, an engine with a little more oomph and a little more tolerance of Intake turbulence, it might have been a world beater. Oh yes, and a lighter weight more compact electronics package would have helped, too.
special ed
1st Sergeant
- 4,857
- May 13, 2018
The B-36 Featherweight program, classified for many years, did not use the J-47 pods as I remember. Now I will have to look it up.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
Maybe get rid of the front armor and fool with the CoG a little bit and...oh, wait...
Alright, enough already! We "Groundhog Warriors" are embarrassed enough as it is. You don't have to rub it in!
I wannabe a "Warthog Warrior" when I grow up...
special ed
1st Sergeant
- 4,857
- May 13, 2018
In 1960 USAFA cadets were at Wright Pat and viewing the outdoor aircraft. One climbed up to look in the B-36 waist blister and seeing the rows of bunks for crew relief exclaimed " It's a flying whorehouse."
I doubt the electronics would have been negotiable, but what kind of changes could have been made to the intake duct?
I've heard of the Featherweight modifications, but I don't know any details of them. If it's declassified, please post what you find.
special ed
1st Sergeant
- 4,857
- May 13, 2018
Internet shows feather weight kept J-47 pods, but years ago Wings or Airpower had a very good article and pictures. I seem to remember there was also featherweight III. The max altitude was in excess of 50,000 feet. A brief bit of trivia: The local hobby shop had a part time helper in the 1980s who was ex-Airforce. Once he and another customer were discussing their respective USAF careers and I heard the clerk say he had been in the featherweight B-36 program. At the time, it meant nothing, but when the magazine Article came out I mentioned it to him and he looked shocked as if I just exposed top secret info.
