Author Topic: "vector rolls"? in T&B combat  (Read 3219 times)

Offline Andy Bush

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"vector rolls"? in T&B combat
« Reply #30 on: May 12, 2000, 02:11:00 PM »
Humble

I don't understand the quote either.

I don't claim to be the expert on BFM but this technique has me confused. The mechanics of what Johnson appears to be saying just don't match up to anything I know in real life.

There are some idiosyncrasies of WW2 a/c that we don't see today...torque effects, for example, that may affect BFM in a manner that a jet would not be able to duplicate. But, I would need to see a more definitive explanation of this maneuver before I become a believer!

Andy

Offline Jekyll

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"vector rolls"? in T&B combat
« Reply #31 on: May 13, 2000, 12:51:00 AM »
 
Quote
The mechanics of what Johnson appears to be saying just don't match up to anything I know in real life.

OK, a quote from 'Thunderbolt!', by Robert S. Johnson (at p. 216)

"The pilot is desperate.  He flings the airplane about, suddenly snaps the Messerschmitt hard over to the left.  No good!  My foot slams down on the rudder, easy on the stick, and the Thunderbolt skids cleanly.  Now - roll!  The P-47 responds like a thoroughbred, flicks around.  Controls back, a sharp turn and the eight guns loom broadside to the target,  One short burst, eight streams of bullets converge, and the Me-110 tears apart".

My reading of this maneuver?  No vector roll, no lag displacement roll.

Imagine Johnson and the bandit are heading due north before the turn begins.  The bandit breaks left.  Johnson hits hard right rudder and skids the Thunderbolt to the right (east), but his aircraft is still pointing north.  He's building lateral displacement which he can use to negate the 47's turn radius deficiency, in effect offsetting the centre of his turn to the outside of the 110's turn centre.

The roll advantage comes in here.  Since the 47 can roll faster than the 110, Johnson can keep his skid going for a longer period of time, and still roll 90 degrees left by the time he reaches the elbow of his opponent's turn.  Had he been flying an aircraft with a slower roll rate, he would have had to break off the skid earlier in order to be wings vertical at the elbow, thus generating less lateral displacement.


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Offline eagl

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"vector rolls"? in T&B combat
« Reply #32 on: May 13, 2000, 06:53:00 AM »
The more I read that passage by Johnson, the more it sounds like a controlled high AOA snap roll or spin entry used to set his initial turn direction.  In the F-15E, we can get an amazing initial turn rate by doing something similiar.  Basically you pre-load the aircraft, either in yaw or pitch, then in the F-15E, you trick the flight control software into snapping the nose abruptly one way or the other.  We can move the nose approximately 25 degrees in pitch, and then can snap the nose almost anywhere around at least a 25 degree cone around our flight path.  This is what we call a "vector roll", rolling (it's actually more like a yaw) around our flight path at an extreme AOA.  The F-22 and F-18 can do this up to and beyond 45 degrees AOA, although the F-18 is thrust limited and can't keep doing it long before it falls out of the sky.

It's possible to do it in WB as well, especially in the P-38 and F4U, but it's difficult.  The P-38 move in the game was perfected by mili then copied by many others.  It's almost impossible to describe, except as a controlled spin entry with the rotation halted after about 180 degrees, then the plane is flown out heading in the other direction.  I haven't tried it in AH because the more lethal guns in AH mean giving your opponent even a snapshot opportunity generally means virtual death.

Back to the P-47...  Imagine this.  The P-47 rudder allows it to skid, say... 10 degrees off of it's actual flight path, in this example to the left.  Once stabilized in that skid to the left, a 90 deg left roll is made.  Guess what?  The plane is now flying along with an instant 10 degrees AOA (the previous slip angle) in a 90 degree left bank, except since he still has a bootfull of rudder, the nose is also pointed an additional 10 degrees down, for a net gain of some 20 deg instant nose position.  This was apparently enough to help put the guns on target.  This kind of thing can be used to combine small nose pointing abilities into relatively large nose position changes and the ability to immediately set the lift vector where it belongs.

On another subject...

Andy, you're right about the new gadgets we have to play with.  We have this new thing called "radio" so the tower can tell us we are allowed to takeoff and land without shooting flares at us, and our "radio" is so high tech that it only has 9 dials, knobs, and switches.  We recently got something called "TACAN", but since that would confuse our poor overloaded students, they put a simple "DME" display on the panel so it only gives range and a radial.  It seems that our old "VOR" still has a few decades of lifecycle still, so they didn't want to tie the "TACAN" to the needles and dials.

The manual describes something called "ADF", but it must cost too much because our jets don't have it installed.  

Isn't it amazing how these modern, 50+ year old planes never seem to get older?  Half of our fleet survived a severe hailstorm, and after some touchup paint they were back flying again.  I guess all the dents on the skin reduce drag just like the dimples on golfballs make them fly farther.

I've already had my moment of final approach Zen...  We were leading a formation approach and Stanley (ya know, Stanley Student) couldn't figure out what power settings to use to keep 110 configured with speedbrake out on final.  It was a warmish spring day, so I told him "quit messing with the throttles, just set 87% and it'll hold 110.  And %76 will hold your 3 degree final just fine too."  It worked as advertised, and as usual he thought it was magic    It's amazing how the little tricks almost ALWAYS work out within a percent, but that's the beauty of the tweet.  I wonder how long it'll be before the new T-6 is known as well.


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Offline Andy Bush

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"vector rolls"? in T&B combat
« Reply #33 on: May 13, 2000, 07:37:00 AM »
Jekyl

Yes, that is exactly how I imagined it. A skid (or something) to increase lateral spacing and then a hard pull before he overshot the extended six of the slower turning bandit.

The 'stuff the stick into the corner' sounded like a lot of bar talk...or somebody was referring to something else.

Thanks for that additional quote..that cleared the matter up.

Andy

Offline Andy Bush

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"vector rolls"? in T&B combat
« Reply #34 on: May 13, 2000, 07:54:00 AM »
Eagl

I know the vector roll that you refer to. The F-4 had an amazing rudder...and we could rotate around the flight path at high alpha as you describe. But you did bleed knots, so the maneuver was great for quick decellerations...like overshooting an F-5 at your six, for example.

When I went to the F-104, I had a surprise waiting for me. On one of my first formation rejoins out of traffic, I cane slamming in as I was used to in the F-4. Then it was idle, boards, and opposite rudder to kill the speed. In the F-4, the thing would come to a shuddering halt. In the F-104, it was a bit different. I had never overshot lead so bad in my life! The 104 rudder was an afterthought and had practically no effect. Vector rolls in the 104 were not very effective as a result...unless you could get enough alpha to pitch the thing up...then it slowed down real well <g>.

I flew Tweets out of Laredo, 69-72. Where are you at?

Andy

Offline eagl

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"vector rolls"? in T&B combat
« Reply #35 on: May 13, 2000, 08:36:00 AM »
I'm at Sheppard AFB, Euro-Nato Joint Jet Pilot Training.  Since the Germans own most of the planes on the ramp, we'll be the last ones to upgrade to the new primary trainer and (I think) our T-38's will also be the last ones to get upgraded as well.  Both the T-6 and new T-38 are supposed to kick bellybutton (as far as trainers go anyhow), but I'm at the wrong base and a few years too soon to see either of them.

If you try using rudder in the F-15E during a rejoin, you're asking for an autoroll if you overshoot.  With cross-controls (aft stick, aileron one way, rudder the other), if you push the stick forward (step 1 in an overshoot) without releasing the rudder first, the plane will get some pitch/yaw/roll coupling and will enter an uncommanded "stabilized" roll all on its own.  Centering the controls is ineffective, and to get out you have to use opposite rudder and hold the stick slightly aft of neutral.  A friend of mine entered an autoroll before the dynamics were fully understood, and during the recovery the stick ended up a little fwd of neutral.  The result was a -7 G pitchover (ouch) that nearly destroyed the plane.  He limped the plane home but repairing it required an almost complete rebuild.  His experience resulted in several new pages in the -1 fully explaining several weird handling characteristics of the F-15E.  

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[This message has been edited by eagl (edited 05-13-2000).]
Everyone I know, goes away, in the end.