Sharknose WHIF

[KJ_Lesnick]

The shark-nose, which was developed for the F-20 allegedly had it's roots in the LERx and nose-strakes used on the YF-17.  

Actual Details
The YF-17 had it's roots in a series of ADF designs in 1965, which were called the N-300 and based on the F-5 except with high-mounted wings which were enlarged and had LERx's above the engine intakes which were rounded and fitted with a conical spike; as time went on, the LERx became larger and more highly swept, the cockpit sprouted more of a bubble-shape, and the intakes were moved further below the LERX.  By now the design was already starting to vaguely look like the YF-17 and retained the original nose the F-5 did which was wider than deep, and shaped in a way that kept a controllable vortex flow off the nose at high alphas making the aircraft hard to spin.

By 1967, the design became the P-530 and the LERx's were substantially enlarged, increased in sweep and made into an ogival shape with a small extension off the front; as time went on the single fin was changed into twin-tails, enlarged, and moved forward with the tailplanes moved all the way aft; the cockpit was moved forward and made into a clear bubble; the conical spikes were replaced with fixed ramps.

As the design progressed into the final design, the extension of the ogival LERx was removed with the chine fully rounded off, and a pair of nose-strakes added instead.  


WHIF Ideas
Imagine if somebody realized that the highly swept extensions off the ogival LERx could be blended into the shark-nose especially coupled with the baseline F-5 nose which was wider than deep: You couple that together and you got a sharknose without too much work.  

The shark-nose would improve directional stability and eliminate the need for two tails and allow a single fin like the the F-20; plus I was thinking that, while two tiny engines worked better than a single large engine for the F-5, it didn't apply to the LWF program (Northrop's own studies indicated this) and a single F100 would have helped their odds in the competition; a chine-shelf could be added on the aft fuselage to maintain the right afterbody width (plus, they look cool).

Another idea I was thinking of was speed -- though I believe the LWF program was right in aiming for high agility over speed.  I was thinking Northrop was also trying to build an export fighter, they were competing head to head with the F-104, which had very good supersonic speed, and agility.  While I wouldn't want to compromise the agility of the plane -- I'm thinking it's possible to make a fixed inlet that allows good supersonic performance (worked for the F-104, and the F-104 was cheap) while retaining good subsonic performance.  The aerodynamics of the aircraft appear as if they'd handle okay when supersonic based on the following criteria

• The aircraft has relaxed stability which means that even when the center of pressure moves aft, it's still not as far aft as normal
  
• The LERx which is angled upwards and features a conical camber might produce more lift up front while supersonic helping mitigate some of the rearwards shift in the center of pressure
  
• While the wing lacks a major sweep and would theoretically suffer a major shift in the center of pressure when supersonic; the overall chord of the wing isn't all that massive compared to a swept-wing or delta-wing (barring the LERx) and though the shift would move the C/L to the 50% mark when supersonic; the chord of the wing is relatively small so the physical length of the shift would be small (so long as most of the mass is distributed throughout the airplane, it shouldn't have a major effect); furthermore low-sweep wings have good supersonic drag.
  
  • The aircraft was designed with differential area ruling (the top area ruled differently than the bottom) which was to improve L/D ratios while maneuvering supersonic of at least 1.2 mach.
    
  ...

[pyro-manic]

F-104, agile?

[KJ_Lesnick]

pyro manic

F-104, agile?

Well this was an F-17 WHIF but regarding the F-104: I was talking predominantly about the high-speed performance of the F-104 (admittedly I'm not truthfully sure of the YF-16 or YF-17 were as fast) as well as it's supersonic agility (probably both instantaneous and sustained) for the following reasons

• While the straight wing experiences a proportional massive shift in the C/L when transitioning to supersonic, the chord of the wing isn't all that massive and the physical shift is small
  
• The distribution of mass throughout the aircraft (some in front and behind the wing) results in a relatively small effect on pitch and trim which allows low trim-drag while supersonic
  
• The fact that the wing is small also further helps this out because a small wing will have less lift shifting aft
  
• The T-tail produces very good leverage subsonic because it's out of the turbulent airflow of the wing, can better ride the downwash, and also has greater leverage being located high up
  
• The T-tail is also fairly large, which means relatively low deflections are needed subsonic and supersonic and a lot of control power is available: This means both good supersonic instantaneous agility low trim-drag
  
• The wing being thin, highly sharp, and straight means low-supersonic drag which yields a surprisingly good L/D ratio supersonic (though lower than subsonic at the same airspeed; the fact is that the difference between subsonic and supersonic is less)
  
• The inlets worked surprisingly well at high-speed despite being fixed geometry which meant high-thrust supersonic (it could cruise supersonic without burners) and the T/W ratio of the plane was very good at pretty much all speeds
  

Admittedly it's subsonic performance could have been better which owed to it's small wings -- technically if it's wings were 10% larger it would have had the best Ps figures of all aircraft in the USAF inventory at the time (I'm not making this up).  

It still performed better than most people would give it credit for at subsonic speed.  Though it's roll authority was a little poor around takeoff and landing, it improved quite a bit as you sped up and it's roll-rate was generally quite good allowing you to keep reversing your turns; though it turned poorly at low-speed but if you got it fast and it was damn near uncatchable, by around 450 and it really came alive and pretty much the faster you got it, the better it maneuvered -- and it stayed good even when you went supersonic; the fact that it was overpowered helped allow lots of vertical maneuvers that were simply beyond that of any other aircraft at the time.  I don't think the F-4 could even keep with it in the vertical.  It could fly surprisingly high even when subsonic -- the minimum maneuvering and stall speeds would probably allow you to get up to nearly 55,000 feet at Mach 0.90 though you'd probably be on a knife edge on those little wings

Regardless, the YF-16 and YF-17 were both way better when it came to sustained and instantaneous turn rates subsonic where it really counts; at least the YF-17 appeared to have some supersonic agility; I'm not sure if either were as good supersonic though as the F-104 or as fast.  The YF-17 was supposed to replace the F-5 and preferably the F-104 all at once.

[KJ_Lesnick]

While I'm at it, did the YF-16 have any advantages with supersonic agility compared to the YF-17 at

- Mach 1.25
- Mach 1.60
- Mach 2.00

I'm curious because of the forward C/L and the inverse camber

[pyro-manic]

Honestly, and I'm not trying to be nasty here, that is a ridiculous question. The only people who would possibly know something like that would be those directly involved in testing, and even then only if such things were specifically tested. Find a book on the LWF programme.

[KJ_Lesnick]

pyro-manic

Honestly, and I'm not trying to be nasty here, that is a ridiculous question.

I'm sorry, I can't post on Secret Projects (they might know) though I'll try and see if I can contact anybody who's a member of both forums and see if I can get them to ask the question there.

BTW: The reason I listed those Mach numbers (for what it's worth) is the following

• The LWF program was focused around maneuverability in the speed range of 0.60 to 0.90, and 0.90 to 1.60
  
• The F-104 seemed to be optimized for Mach 1.4 and had good agility up to Mach 2
  
• The YF-17's conically cambered chine would produce low-trim-drag, and thin, low-sweep wings look like they'd produce low-supersonic drag similar to the F-104
  
• The F-16 has an inverse camber with the flaps up which also yields a good L/D ratio, and the chine would produce a benefit while supersonic combined with it's C/G position
  

I just wanted to see who would perform better supersonic aerodynamically.