# Avionics & Performance



## Zipper730 (Dec 6, 2018)

I'm curious how the performance and avionics of the following aircraft compared with each other

English Electric Lightning F.2/F.3/F.6
Lockheed F-104A/C and F-104G
Saab J-35 Draken
Convair F-106A


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## Zipper730 (Dec 11, 2018)

From what I've read about the performance, I would assume the Lightning would have the best acceleration but shorter range and about the same top-speed as the F-104's; the F-106A, from what I recall was slower than the previous two. As for the J-35: Some said it performed as well as the F-104, and others merely said that both could operate in the Mach 2+ range (with a way shorter takeoff run).

Avionics, I was told the F-106 was the best until it was basically retired, the lightning was said to be sophisticated by some, others described it as rather simple but had good human factors characteristics (HOTAS). The F-104G actually had a decent radar for interception from what I was told, the F-104A/C were fairly primitive and heavily dependent on SAGE.

I'm not sure how the J-35 compared in terms of onboard avionics but it did essentially profit from a very sophisticated datalink.

Anybody have anything that would provide more accurate data on the matter, provided it's not classified


G
 Glider


 GrauGeist

X
 XBe02Drvr


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## XBe02Drvr (Dec 11, 2018)

Zipper730 said:


> I would assume the Lightning would have the best acceleration but shorter range and about the same top-speed as the F-104's





Zipper730 said:


> As for the J-35: Some said it performed as well as the F-104, and others merely said that both could operate in the Mach 2+ range (with a way shorter takeoff run).


The early F104s, the Lightning, the MIG21, and the J35 were more or less contemporaries, were inspired by the advent of long range jet powered nuclear bombers, and were essentially point defense interceptors with a ME163-like mission profile.
The standout in this class, it seems to me, is the J35, with its STOL rough field capability (shared with the MIG), its ACM maneuverability (shared with the Lightning), its versatile avionics with ground attack capability, and its fuel capacity and flight endurance (shared with no others).
Given the technology of the time, interceptor designers tended to go with the "missile with a man in it" approach, resulting in clipped wing lawn darts like the MIG21 and F104.
The Swedes, OTOH, could only afford one aircraft type per generation and needed to defend their mountain kingdom from all potential adversaries, so they went with a radical airframe design and created a multi-talented interceptor.
When you get into the Mach 2 range, top speed doesn't really have much significance. What's far more important is the rate of acceleration getting there. By the time any of these aircraft (except the J35) have reached Mach 2 they're at bingo fuel. It's a long, slow, thirsty slog from .95 to 2.0, and the practical limit is not how fast your airframe will fly, but how long your canopy can stand the heat before melting.
The F104G was a politically driven unwise attempt to convert a lawn dart into a multi-role fighter, which resulted in too much fancy equipment being crammed into an airframe that wasn't suited to it to perform missions the airframe wasn't designed for. Result? Lots of dead Luftwaffe pilots. Lawn darts don't make good Close Air Support birds.
Cheers,
WES


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## Glider (Dec 11, 2018)

I have to give the nod to the Lightning which for its time was sophisticated and had a blistering performance

There were a number of problems with the Lightning first prototype, the sort that the RAF were delighted to have:-
a) Roll rate had to be restricted to 180 deg/sec because of the pressure that built up in the fuel tanks. _I have to admit that 180 sounds like a decent roll rate to me_
b) Acceleration was rapid and care had to be taken until the pilot was used to it
c) Speed was such that flight limitations had to be increased to mach 1.3. and straight line acceleration had to be limited to 5g (subsonic) and 3g Supersonic. _Now that's what I call acceleration_
d) The rapid rate of climb was too much for the instruments which had to be replaced

What I find so impressive is that *this first prototype didn't have afterburners*


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## Zipper730 (Dec 11, 2018)

XBe02Drvr said:


> The early F104s, the Lightning, the MIG21, and the J35 were more or less contemporaries, were inspired by the advent of long range jet powered nuclear bombers, and were essentially point defense interceptors


Yes


> The standout in this class, it seems to me, is the J35, with its STOL rough field capability (shared with the MIG), its ACM maneuverability (shared with the Lightning), its versatile avionics with ground attack capability, and its fuel capacity and flight endurance (shared with no others).


Out of curiosity, how much fuel capacity did it have?


> When you get into the Mach 2 range, top speed doesn't really have much significance. What's far more important is the rate of acceleration getting there. . . . It's a long, slow, thirsty slog from .95 to 2.0, and the practical limit is not how fast your airframe will fly, but how long your canopy can stand the heat before melting.


The Lightning probably had everybody beat in time to Mach 2.0, not sure how the J-35 and F-104 compared, I assume the F-106 didn't accelerate as fast (I do remember hearing something to the effect of 4 minutes to Mach 2.0, though I do not remember the exact details). I didn't know what aircraft had canopy failure issues other than the F-4...


> The F104G was a politically driven unwise attempt to convert a lawn dart into a multi-role fighter, which resulted in too much fancy equipment being crammed into an airframe that wasn't suited to it to perform missions the airframe wasn't designed for. Result? Lots of dead Luftwaffe pilots. Lawn darts don't make good Close Air Support birds.


But it's radar was decent...



Glider said:


> I have to give the nod to the Lightning which for its time was sophisticated and had a blistering performance


I'm not sure how the capabilities of the radar ranked with other aircraft, but I do know human factors were excellent. The acceleration and climb were out of this world.


> There were a number of problems with the Lightning first prototype, the sort that the RAF were delighted to have:-
> a) Roll rate had to be restricted to 180 deg/sec because of the pressure that built up in the fuel tanks. _I have to admit that 180 sounds like a decent roll rate to me_
> b) Acceleration was rapid and care had to be taken until the pilot was used to it
> c) Speed was such that flight limitations had to be increased to mach 1.3. and straight line acceleration had to be limited to 5g (subsonic) and 3g Supersonic. _Now that's what I call acceleration_
> d) The rapid rate of climb was too much for the instruments which had to be replaced


I assume some of these issues were rectified?


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## Glider (Dec 11, 2018)

I will do some research into the radar tomorrow but one of my favourite facts was the interception of a U2 at over 68000 ft by an F1 lightning in (I think) 1963. The biggest problem being that the U2 was so much slower.

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## XBe02Drvr (Dec 12, 2018)

Zipper730 said:


> I didn't know what aircraft had canopy failure issues other than the F4.


They all did to a greater or lesser extent if they pushed the issue too much. Plexiglass is plexiglass is plexiglass, no matter what airframe you mount it on. I read somewhere that "A frame" canopies like F102, F106, Mig25, X15, SR71, etc were more resistant to this issue, though more restrictive to visibility from a combat standpoint.
Cheers,
Wes


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## Zipper730 (May 13, 2019)

XBe02Drvr said:


> They all did to a greater or lesser extent if they pushed the issue too much. Plexiglass is plexiglass is plexiglass, no matter what airframe you mount it on.


Why didn't they create a different form of glass?


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## XBe02Drvr (May 14, 2019)

Zipper730 said:


> Why didn't they create a different form of glass?


They did, for the X15 and the SR71, but those aren't really practical for a mass produced combat aircraft. The trade-offs are visibility, durability, affordability, and availability of exotic materials. Those that exceeded the Mach 2.? limit for any length of time (X15, SR71, MiG25) all suffered from reduced all around visibility from the cockpit, that could be (and was for the MiG25) detrimental in a combat situation.
Cheers,
Wes


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## Zipper730 (May 14, 2019)

XBe02Drvr said:


> They did, for the X15 and the SR71, but those aren't really practical for a mass produced combat aircraft.


True, but what you said about the MiG-21 largely has to do with the fact that the canopy appears small and isn't raised up much (so pretty poor visibility to the rear), the framing is a little bit large, but doesn't seem too bad.

The F-15 however was designed for the same top-end speed as the MiG-25 (you'd have to hit the VMax switch), the canopy was a bit weak, but they had proposed fixes. The problem wasn't the physical ability to fix it, but the lack of will to pay for it (the F-15 was very expensive, and already the subject of cuts).


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## tyrodtom (May 14, 2019)

Zipper730 said:


> Why didn't they create a different form of glass?



Plexiglass isn't glass, it's a clear acrylic plastic.
But it's a thermoplastic, so no matter how thick you make it at some point it's going to be affected by aeroheating.
They've developed better thermoplastcs, as speeds increased , I'm sure.


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