Republic F-84 Thunderjet & Thunderstreak: Prototypes and Projects

 
What was this,

Republic MX-1483 Floating wing tips on F-84 ?.
 
Range extender/load alleviation I guess? Sounds like a similar concept investigated and flight tested by Airbus about ten years ago.
 
The “floating wingtip” idea from which Project Tip-Tow evolved had originally been developed by Richard Vogt, a German aeronautical engineer known for unusual, off-the-wall concepts. Vogt’s idea was a way of having one’s aerodynamic cake and eating it too: By extending the overall aspect ratio of an airplane’s wing, floating wing panels would add lift and improve aerodynamic efficiency, and could carry extra fuel. Yet because they wouldn’t be firmly attached to the aircraft structure and would support themselves by aerodynamic lift, the panels wouldn’t increase wing loading. Theoretically, Vogt’s concept could be extended beyond floating wing panels to encompass entire aircraft serving as “wing extensions.”
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https://www.militarytimes.com/off-d...d-pilots-tip-towing-on-the-verge-of-disaster/
 
Incidentally I think the floating wingtip was flight-tested in period on a Beech twin (and others IIRC). The MX Project doesn't sound like Tip-Tow.
 
@hesham : noticed you reaction with a dissatisfied smiley. Is there something wrong?

@Sabrejet : Tip-Tow (in its non-rigid link application) is a direct application of the floating wing (see quote above).
 
hesham said:
I think that's not the meaning of setnese,floating wingtip.
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It is. The term "floating wingtips" has a number of contexts. But, in the 1950s, it simply referred to wingtip attachment points which allowed flexing/non-fixed wing extensions (in this case, provided by 'parasite' fighters). These parasites retained a degree of manoeurability (mainly through their elevators) for attitude corrects while still contributing to overall lift.

Those "floating wingtip" attachments were but one method of Wingtip-Docked Formation coupling (as well as a potential way to mount/tow extended-range tanks). But the B-29A/F-84Ds combo shown represented Project 'Tip Tow' or MX-1016 ... which the follow sources repeats as the typo 'MX-1018' [sic].

In the summer of 1950, the next set of wingtip coupling experiments were ready to be flight tested, known as Project MX 1018 or Tip Tow. The Republic Aviation Corporation of Long Island, NY had modified a B-29A bomber and two straight-wing F-84D fighter jets. The outer wing panels of the B-29 were replaced with a towing or retrieving mechanism, similar to the C-47/Q-14 mechanism in that it had a lance device and an extended capture piece associated with it. It consisted of a hydraulically actuated cylinder or retractable boom that would extend out from the wing of the B-29, the F-84 then flew forward with a lance to hook up to the receiver at the end of the boom. The connection would lock (though motion
in pitch, roll, and yaw was viable) and then pull the F-84 in to be locked at an aft position, that had been rubber sealed. At that point, the F-84 was only capable of roll about the longitudinal axis for the wingtip connection. The capability to roll about this longitudinal axis is the aforementioned flapping motion. It was hoped that a simple method relating the lance rotation or flap angle to elevator movement could provide automated flight control.
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Source: Compound Aircraft Transport Study: Wingtip-Docking Compared to Formation Flight, Samantha A. Magill (dissertation for Virginia Polytechnic Institute and State University PhD in Aerospace Engineering, page 13.

Project MX-1016 'Tip Tow' was another Wingtip-Docked Formation concept demonstrator eventually leading to Project 'Tom Tom' with a B-36. [1] Alas, I can find no online link between Project 'Tom Tom' and MX-1483. So, the question remains: What was the exact nature of the "floating wingtips" proposed for the USAF's Project MX-1483?

______________________________

[1] Note that Designation-Systems.Net has MX-1016 listed as 'Tom Tom'
-- https://www.designation-systems.net/usmilav/mx/1000-1499.html
 
Well I suspect they are linked to the Beech twin tests I mentioned; those were floating wingtips as distinct from Tom-Tom. Though related I see them with different aims: Tom-Tom was more to do with the benefits of carrying escort fighters in this way whereas I'd expect a "floating wingtip" to be more for load alleviation and range extension. I may be mis-remembering things but I'm sure that carriage of fuel in (jettisonable?) floating wingtips was proposed too.

As mentioned, Airbus has more recently looked into these benefits and I know a scale model was flight tested by them and also recall an A340 being configured for full-scale testing.
 
 

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Sabrejet said:
Well I suspect they are linked to the Beech twin tests I mentioned; those were floating wingtips as distinct from Tom-Tom. Though related I see them with different aims: Tom-Tom was more to do with the benefits of carrying escort fighters in this way whereas I'd expect a "floating wingtip" to be more for load alleviation and range extension. I may be mis-remembering things but I'm sure that carriage of fuel in (jettisonable?) floating wingtips was proposed too...
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Indeed. As I mentioned, "floating wingtips" has a number of contexts. The Beechcraft contract was for Project 'Long Tom' where a Beech L-23 Seminole was fitted "with small fuel-carrying wingtip 'floating panel' extensions" for tests during 1955-56.
 
A very interesting article on the XF-84H's propulsion:
https://www.enginehistory.org/GasTurbines/Allison/XF-84/XF-84.shtml
I was not aware that the Allison T54 (double T56) was intended for the third unbuilt XF-84H, and that Allison developed afterburning T40 and T54s! The afterburning turboprops traded shaft horsepower for thrust; ultimately not worth pursuing...

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Hi! XF-84H flight test movie.
F-0281 XF-84, F-105 Flight at Edwards Air

The Republic XF-84H Thunderscreech is considered the loudest aircraft ever built.Its propeller blades rotated faster than the speed of sound, even at idle. They were so loud that the noise could be heard from up to 25 miles away.The constant sonic booms would make ground crews sick, and one crew member even had a seizure.The Thunderscreech first flew in July 1955. The program was canceled after just seven flying hours.
 
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Basil said:
The afterburning turboprops traded shaft horsepower for thrust; ultimately not worth pursuing...

View attachment 796319
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Afaik, there was no variable afterburner exhaust nozzle, so the additional afterburner back pressurre on the turbine caused a drop in shaft horsepower.
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*Facepalm*


blackkite said:
Hi! XF-84H flight test movie.
F-0281 XF-84, F-105 Flight at Edwards Air

The Republic XF-84H Thunderscreech is considered the loudest aircraft ever built.Its propeller blades rotated faster than the speed of sound, even at idle. They were so loud that the noise could be heard from up to 25 miles away.The constant sonic booms would make ground crews sick, and one crew member even had a seizure.The Thunderscreech first flew in July 1955. The program was canceled after just seven flying hours.
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The first test pilot even told the engineers "There's not enough of you and you're not big enough to put me back into that plane"

You'd have to get really creative to make the shockwaves quiet enough to not concuss your pilot into early-onset dementia.
 
Scott Kenny said:
*Facepalm*



The first test pilot even told the engineers "There's not enough of you and you're not big enough to put me back into that plane"

You'd have to get really creative to make the shockwaves quiet enough to not concuss your pilot into early-onset dementia.
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I am sure it was a really loud aircraft but I would not be surprised if all these stories are a little bit exaggerated. There are other propeller aircrafts where the propeller tips go supersonic under certain conditions. The XF-88 was also tested with a supersonic propeller and there are no comparable dramatic stories about it.
 
Basil said:
I am sure it was a really loud aircraft but I would not be surprised if all these stories are a little bit exaggerated. There are other propeller aircrafts where the propeller tips go supersonic under certain conditions. The XF-88 was also tested with a supersonic propeller and there are no comparable dramatic stories about it.
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I was fortunate to see a tape with audio of the Thunderscreech many, many years ago. Its effect on the ears and well being was not understated. The airframe should have been declared illegal after the first run-up due to it being a significant health hazard!!! If they had them during Vietnam, a 4 ship low pass over the jungle would have caused the Cong running out of the jungle with white flags!
 
Basil said:
I am sure it was a really loud aircraft but I would not be surprised if all these stories are a little bit exaggerated. There are other propeller aircrafts where the propeller tips go supersonic under certain conditions. The XF-88 was also tested with a supersonic propeller and there are no comparable dramatic stories about it.
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The Thunderscreech's idea was to make the entire blade supersonic, from root to tip.
 
ISTR reading somewhere ( but where ? ) that the major problem with the XT40 was the combining gearbox . Apparently , both T38 power sections drove into a single 'bull gear' output gear , and the metallurgy of the day couldn't produce a part that could take the combined load without failing . . .

cheers,
Robin.
 
The Republic XF-84H's official maximum speed was 520 mph (approximately 837 km/h), but its theoretical design speed was expected to reach 670 mph (approximately 1,078 km/h), making it the fastest propeller aircraft in the world. However, this design speed was never reached, and development was discontinued due to the excessive noise and vibration caused by the propeller blade tips exceeding the speed of sound.

Official Record: 520 mph (approximately 837 km/h)
Theoretical Design Speed: 670 mph (approximately 1,078 km/h)
Actual Flight Speed: Although some reports suggest that the actual speed was lower than expected, reaching a maximum of around 450 mph, the official maximum speed was 520 mph.

(AI)
 
Basil said:
I am sure it was a really loud aircraft but I would not be surprised if all these stories are a little bit exaggerated. There are other propeller aircrafts where the propeller tips go supersonic under certain conditions. The XF-88 was also tested with a supersonic propeller and there are no comparable dramatic stories about it.
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Curiously, I can't recall many accounts of the XF-88 prop testbed that don't mention the horrendous noise.
 
Sabrejet said:
Am I the only one who views YouTube videos as trash?
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Not all but, most with commentary seem to demonstrate the worst forms of, "Someone told me this so you have to believe me". Definitely no standard for standards at all.
All in the name of "Get me on the vid so I can look cool" mentality, like pretenders on the idiot box pretending the world has to listen to them.
 

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