Multirole F-106

[LostCosmonaut]

The F-106 (bane of Canadian nationalists everywhere) had a quite long and successful career as an interceptor. However, could it have been turned into an air superiority fighter or multirole aircraft?

 

Consider the Following

 

F-106 wing loading at MTOW: ~309 kg/m^2

F-4 wing loading at MTOW: ~569 kg/m^2

 

F-106 Thrust/Weight Ratio (At MTOW with full afterburner): ~.576

F-4 Thrust/Weight Ratio (At MTOW with full afterburner): ~.578

 

While this is a very cursory examination, the low wing loading of the F-106 indicates that it would have good turn performance. I have seen anecdotal evidence confirming this, although I have also heard that it lost energy very quickly in sustained turns (I have heard similar about the MiG-21, which also utilized a delta planform).

 

One of the primary issues I see with turning the F-106 into an air superiority fighter was its weaponry. To put it charitably, the AIM-4's perfromance against maneuvering targets was ass. Most likely, modifications would be needed to enable carriage of the AIM-9. I have no experience on the matter, but I do not see any unsurmountable obstacles. As far as air-to-ground munitions go, the F-106 is somewhat lacking in payload compared to aircraft such as the Phantom. However, at least theoretically;

 

 

Overall, while it wouldn't have been perfect, in a world where the Phantom doesn't exist, or isn't used by the USAF, the -106 could have been made into a passable multirole aircraft.

[xthetenth]

If I remember right part of the problem is that it was an AIM-4 armed interceptor back when avionics really couldn't be changed easily. So fitting it for everything else would be a non-trivial problem.

[Sturgeon]

I think you would have been mostly limited in takeoff run distance, especially with a good payload. This is why you see about zero multirole delta winged birds until relaxed stability becomes a thing. This means while the F-106 is an excellent interceptor, when you try to deploy it with a bunch of bombs and shit on a forward airbase it doesn't do so well.

Especially when it's hot.

And humid.

[Collimatrix]

Deltas have very good wing loading, but ass span loading.  Span loading, or the ratio of the mass of the aircraft to its wingspan, is an important factor in subsonic maneuverability.  Induced drag is a function of the square of span loading, so as you can imagine, deltas are really hurting here.

 

Overall, it sounds like you're proposing basically a bigger mirage III.

[LostCosmonaut]

Deltas have very good wing loading, but ass span loading.  Span loading, or the ratio of the mass of the aircraft to its wingspan, is an important factor in subsonic maneuverability.  Induced drag is a function of the square of span loading, so as you can imagine, deltas are really hurting here.

 

Overall, it sounds like you're proposing basically a bigger mirage III.

 

The point about span loading would explain what I've heard about the -106 bleeding energy in turns.

 

As far as being a bigger Mirage III, that seems like it'd be pretty already. From what I know, the Mirage III was an alright plane (which underwent quite a bit of development throughout its life). That also brings to mind export possibilities (though any export variants would have had to have had the SAGE equipment removed or not fitted in the first place).

[xthetenth]

That would explain why the asymmetrical training experiences regarding the plane put its successes in the "experienced instructor manages to catch pilot who hasn't seen it before unaware with a tricky maneuver or somehow they talked the referees into letting them take off with Genies".

 

As far as the accounts I've read, I remember this one.

[Collimatrix]

This helpful educational video from Handley Page (from back when educational videos were worth a damn) explains, among other things, the weakness of delta wings:

 

 

(go to 7:30 if you're impatient)

They've simplified things a bit, but basically delta wings generate very high induced drag, which is a major consideration in subsonic.

 

That could be a problem for a multi-role platform, although the mirages seem to have gotten along OK.  I think it is worth noting that in the absence of unstable designs with FBW, Dassault quit the delta for a tailed, swept-wing design and was looking into swing wings.

[LostCosmonaut]

Since any hypothetical multirole F-106 (or derivative thereof) would most likely be used in lieu of Phantoms, it is somewhat pertinent that Iran has been getting some use out of their F-4s lately; http://foxtrotalpha.jalopnik.com/breaking-iranian-f-4-phantoms-wade-into-the-anti-isis-1665411308/1665479531/+damon

[Collimatrix]

Having re-read the relevant passage in Design for Air Combat, part of the reason Dassault ditched pure deltas on the mirage F1 is that pure, stable deltas have rather poor runway performance, and high takeoff and landing speeds.

 

Deltas have low aspect ratios and high leading edge sweep, so they're not so great at generating lift.  This means they have to be flown either at high AoA or high speed to generate sufficient lift for takeoff.  Also, using flaps is out on tailless deltas because there's no way to trim out the nose-down moment the flaps would generate.  Super high AoA is out; the pilot can't see anything and the tail will bonk into the tarmac, so pure stable deltas usually had high takeoff and landing speeds, and lengthy takeoff and landing lengths.

 

There is also a reduction in lift during rotation, since the elevons have to push the tail down to bring the nose up.  In addition to providing torque, this action is also providing downforce.

 

Instability goes a long way to curing this, naturally.  Mirage 2000 has a landing speed of 260 KMH vs 330 KMH for the mirage III.