Depressible Pipper

[DonH]

Was trying to understand the Depressible Pipper in the A-10C.

 

A Red River Rat sent me this from his days flying Strikes in F-105 over RP-1/Hanoi during the early years of the Vietnam WAR.

 

His callsign: Thud

 

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Re: Depressible gunsight pipper?

 

I don't remember too much about the specifics of "my" F-105 gun-sight - - it was long ago :-D .

When I first started flying the F-105 it had just a plain depressible pipper. We would do similar to what you are doing - based upon dive angle plus release altitude (would give us slant range to the tgt) and airspeed we would use a chart to provide depression angle which we would set in to the gun-sight before takeoff. Since we always would strive for the same parameters on the bomb run it was always the same and hence we only needed to determine it once. In combat we would roll in from about 14,000 ft, dive at 45*/550 kts and release at 8000 ft (so that we could pull out by 4000 ft and stay above the rapid fire (23mm and below) ground fired defenses). In training we would dive at 30*/450 kts and release at 4000 ft to pull out by 2000 ft - this of course required a different depression setting. We would roll in - come back to idle power - establish dive angle (45* doesn't sound like too steep if you set out a protractor but from 14,000 ft it feels like almost straight down) - adjust for airspeed (with two 3000 lb bridge busters and a slick centerline fuel drop tank, we would have to deploy speed brakes or we would end up supersonic by the time we reached release, thereby completely screwing up the release and bomb ballistics - six 750 lb bombs with two wing fuel drop tanks didn't require speed brakes because of the extra drag). The dive angle was the hardest thing to get used to but became second nature and only required very minor adjustment during the bomb run. Airspeed required more attention and the biggest error parameter was the forecast wind offset - if the wind was forecast to have a crosswind parameter we would have to calculate (before take-off) how much upwind pipper offset would be required at release - likewise for the short/long downwind/upwind component. (We would pull of the Paul Doumer bridge across the Red River in downtown Hanoi a see a nice string of bombs 50 ft one side or the other and know that they had blown the wind forecast and that we were going to have to do it all over again tomorrow or soon thereafter. It that case we prayed for the mis-aimed bomb that was 50 ft off and by luck just happened to drop a span.) Just before the 8000 ft drop point - got there very quickly - we had time for one quick correction because at the point of release we had to have no rudder, aileron or pitch input for the bomb to go where the pipper was located. Then to pull out by 4000 ft it took 4.5 to 5 gs to get the nose above the horizon, then speed brake in - afterburner full - jinx - and egress supersonic.

Of interest was the fact that if the Master Arm switch was on we could hit a button on the stick and the gun-sight would revert to the gun air to air lead computing sight picture (in case we were jumped by Migs we wouldn't have to mess with switch and depression settings to fire the gun) - another click of the button would put it back to the preset bomb setting. While no-one would admit it, except maybe at the bar, there were a number of bomb hits many hundreds of ft off target that were obvious bomb runs with an air to air pipper setting. It was easy to tell if you had such a case during the dive - but too late to do anything about it except put in a bunch of "Kentucky Windage".

Later during my tour someone came up with the smart idea of using the air to ground radar to get an accurate slant range - then by enabling a movable air to ground pipper we got a crude Continuous Computing Sight in pitch only - kind of like the F-16 sight you are familiar with. This really helped if the Force Commander misjudged the force roll-in point requiring a dive angle different than the desired 45*.

Strafing was similar except we had differing dive angles precomputed to memory. Then if we wanted to make a high angle strafing run (30*) to stay above ground fire as long as possible we had one setting to dial in or for a low threat, low angle run (10*) another setting. Rockets were another setting for I believe a 20* dive angle. After leaving the States for SEA we never thought about or carried rockets.

[probad]

love to hear his thoughts on our community that can't seem to do anything without a cbu-105