Braking techniques

Operating an F-16 on the ground or in the air - from the engine start sequence, over replacing a wing, to aerial refueling procedures
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outlaw162

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Unread post24 Apr 2008, 03:25

Interesting subject, slowing & stopping high-speed tri-cycles.

If you no-chute(d) the F-100, and waited ‘till 100 knots to lean on the brakes, anti-skid usually didn’t cycle, and you probably wouldn’t have heated ‘em up enough to need the fans (I don’t know if they still use fans, maybe like foaming runways, they don’t need to do it anymore). And these were low tech brakes.
The 100 had the stab authority to “aerobrake”, but aero braking was not done because:
1. You would grind thru the tailskid boot and thru a portion of the actuator “door”.
2. If there was a significant x-wind, the Hun would weathervane instantly if you DID use the chute, and you needed the nose wheel down prior to chute deployment to counter the “head for the grass tendency” with NWS. Good news, if the runway was wet, even though the aircraft would weathervane, it would probably hydroplane & momentum would keep it tracking right down the centerline. Bad news, it could take 9,000+ feet to straighten it out and stop it.
In any case, with the 100, it crossed the fence at 155-165 (D), 175-185 (C) & the nose was put down immediately after touchdown & NWS engaged, then drag chute.

If you no-chute(d) the F-105, the aerobraking was extremely effective and probably resulted in the most TOTAL number of knots being lost (before the nose fell thru) of any fighter. Problem here was you crossed the fence at 190+, with a lot of TOTAL knots to lose, and a no-chute still took 7000-8000 feet to stop, but once again you could lean on the brakes at 100 knots and not heat ‘em up enough to need the fans.
With the Thud, combination of drag chute and aero braking resulted in an impressive deceleration, rarely needed the wheel brakes.

The A-7 was always a no-chute and if you flew the FPM to touchdown you killed a lot of knots at impact (you crossed the fence fairly slow anyway, 130-140ish, I don’t remember the AOA, 17.5?). It could also be “flared” (and aerobraked) like a real aircraft if you could live with the increased frequency of MG tire changes due to the uneven wear on the outboard portion of the tires.
USAF “D” had good brakes (Navy “E”, different, not so good) and once again, you couldn’t heat ‘em up too much from 100 knots on down (longer you could wait, the better).

F-4, same thing on a no-chute. If you could afford to wait ‘till 100 knots on the brakes, you wouldn’t build up enough heat to prevent you from being cleared thru the “Octagon” (hot pit refueling) at Miramar. (crossed the fence 145-155, (TE BLC capped), steady AOA tone, once again the number escapes me, 17.5 again?, and if you used the chute, you could pull the chute just prior to touchdown for max stopping.)

F-16A crossed the fence so slow (130ish) and aerobrakes so well, I wasn’t even sure why it had wheel brakes, other than to stop on the ramp.

The whole stopping/planning process changed somewhat x-country at Buckley. Always had the hook though.
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JpoLgr

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Unread post26 Apr 2008, 14:41

outlaw162 wrote:The A-7 was always a no-chute and if you flew the FPM to touchdown you killed a lot of knots at impact (you crossed the fence fairly slow anyway, 130-140ish, I don’t remember the AOA, 17.5?).


You're right on the AoA, but it doesn't refer to degrees(it refers to "units AoA") so it's not directly comparable to modern AoA readings.


outlaw162 wrote:F-16A crossed the fence so slow (130ish)


Newer vipers are faster on the approach and cross the fence at 150+ Kcas.


Cheers.
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Gums

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Unread post26 Apr 2008, 17:54

Salute!

Great to see some folks that have used the brakes in several jets.

We need more "informed" folks to pitch in here.

************

The original Vipers crossed the overrun at 130+ a bit.

The SLUF was about the same.

No problems with either if you stayed off the wheel brakes until below 90 knots or so, unless heavy. Mass still needs to be accounted for, but the speed is the most important thing WRT brake energy limits and heat.

SLUF did not aerobrake nearly as well as the Viper.

I flew the Deuce and the VooDoo. Both of those aerobraked really well. We had a chute for the VooDoo, as we came down final at 175 knots plus 5 knots for each 1000 pounds of gas above 3,000.

The Norwegians talked with us about the chute for the Viper. In those pre-cambrian days, they were the only ones with a chute, best I recall. Had to do with ice on the rnwy and the immense idle thrust for a light plane. Biggest problem was using the chute in a crosswind. Could go off the rnwy real quick.

In my career, I only blew two tires. One when I couldn't stand the Vee student in the A-37 and "helped" him with brakes. My pressure added to his pressure and we locked up one and it blew! Was hard to live that one down after the tow to the ramp, heh heh. the other was in a SLUF when the brake valve stuck, locking the wheel. I had a bad habit of tapping the brakes to see if I could get some feedback/pressure. It bit me in the a$$$$, and I soon had an inadvertant mid-field barrier engagement. Kept it on the rnwy and we got the wheel well fire out without losing the jet.


later,

Gums sends ....
Gums
Viper pilot '79
"God in your guts, good men at your back, wings that stay on - and Tally Ho!"
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outlaw162

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Unread post27 Apr 2008, 03:05

Would have loved to have flown the newer Vipers of course, but only flew the block 15 & small tail block 10 A’s & B’s for a couple of years in the twilight of my undistinguished military flying.

Never checked out in the F-101, but got a couple of rides, one in the backseat of a “B” (no stick, but a foot actuated mic switch that reminded me of 50’s/60’s automobile bright/dim headlights switch on the floor) and one in the back of an “F” (with stick). Cool airplane (hard light J-57 AB’s never quite lit at the same time, like an F-100 formation takeoff), and I have been told that the microwave oven was developed from technology used for the 101’s variable tune magnetron in the radar. We can thank the Voodoo for many of our hot lunches. Didn’t care for the constant pressure breathing.

Never blew a tire (squared a few), never took a departure end cable or net. A couple of approach end engagements in the F-4 & A-7 (pretty normal for hydraulic stuff) and one approach end arrestment in the F-16 (electrical, naturally). At the time, I was told it was a bit unusual since there hadn’t been but maybe a couple up to that point. I can’t verify that however. If I recall correctly, the big concern was getting the nose wheel down and gingerly holding it down before reaching the cable with limited side-stick feedback as to how much nose-down force (you could evidently generate too much) was actually being put on the somewhat “delicate” nose gear assembly. But I could be wrong.
Last edited by outlaw162 on 27 Apr 2008, 13:41, edited 1 time in total.
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johnwill

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Unread post27 Apr 2008, 06:18

outlaw162, you were wise to no put too much pressure on the nose gear before cable engagement, for two reasons. First, it wasn't necessary. The hook engagement geometry is based on nose gear on the ground so the hook load will slightly try to pull the nose gear down. But if the cable is engaged with the nose gear at aero braking pitch angle (around 10 deg) the hook load will slam the nose gear down and possibly fail it.

The second reason is the one you feared, failing the nose gear from overloading it. That actually happened sometime around 1979 at Edwards. The pilot, call him "Dave", was practicing for an air show takeoff where he wanted to stay on the runway as long as possible, make an abrupt rotation and have enough airspeed to make an impressive high g transition into a climb. So he pushed forward so hard at such a high speed, the horizontal tail lifted the main gear off the ground, thus overloading the nose gear and it broke. "Dave" rapidly realized what happened and took off before other failures occurred, like plowing the runway with the radome and inlet. He safely landed on the lakebed, but ground away much of the forward electronics bay and the inlet lip. Later, the airplane was given a new 2 seat forward fuselage, new delta wings, and two fuselage plugs to become F-16 XL No. 2.
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Unread post27 Apr 2008, 15:44

Salute!

Hey, john-boy! We call the phenomena "wheel-barrowing" when you have so much lift behind the nose gear that the mains raise off the concrete.

I learned the hard way about hook point angle in the SLUF and missed the departure barrier after screwing up my breaking on a slick runway. Was holding the pedals down and taking what I could from anti-skid, but I decided to put the hook down "just in case". Missed the cable, GASP! So off the brakes at about 60-70 knots and pull back a bit for better hook angle and snagged the aircraft carrier boat chain doofer on the overrrun and came to a smooth halt. Hard to live that one down, but I was a rookie in the jet and they forgave me. Also found a mal in the anti-skid.

The Viper JTF folks said the hook had a great angle, and not to pull back or push forward. Lower nose and don't aerobrake and don't use brakes. We had some high-speed heavy arrestments when motors acted up on takeoff. All were great.

The big lesson here for the yutes is to wait until you can't stand it, then use the brakes. The higher your speed when you use them, the more heat, the more wear, the more problems.

out,

Gums sends ....

P.S. The older jets' anit-skid completely released when skidding. The ones we now have are very smooth and I tink they are supposed to give you a "20% rolling skid" or something like that.
Gums
Viper pilot '79
"God in your guts, good men at your back, wings that stay on - and Tally Ho!"
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JpoLgr

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Unread post27 Apr 2008, 16:01

Gums wrote:The Norwegians talked with us about the chute for the Viper. In those pre-cambrian days, they were the only ones with a chute, best I recall. Had to do with ice on the rnwy and the immense idle thrust for a light plane. Biggest problem was using the chute in a crosswind. Could go off the rnwy real quick.


In Greece all vipers (Blk30/50/52+) have chutes only for emergency use. Crosswind is still a problem in chute deployment :wink:


Gums wrote:...in a SLUF...Kept it on the rnwy...


Gums, check this out: (2007)
http://www.youtube.com/watch?v=5UxG6cJcLuU
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JpoLgr

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Unread post27 Apr 2008, 16:08

johnwill wrote: That actually happened sometime around 1979 at Edwards[...]Later, the airplane was given a new 2 seat forward fuselage, new delta wings, and two fuselage plugs to become F-16 XL No. 2.


Now that's a jet with a story to tell! Thanks for sharing.
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johnwill

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Unread post28 Apr 2008, 01:11

All of you with hands-on familiarity with the F-16 will know what I'm talking about. The hook shank is a flat curved strap to follow the fuselage contour and the hook point fits into a cavity. All to reduce drag, supposedly. When we did the arrestment tests on F-16A No. 2 in '79, the hook would sometimes slam into the fuselage and do some locally heavy damage. They added a semi-hard rubber block to the back of the shank just above the hook point and some local beefup to the fuselage around the cavity. Didn't totally solve the problem, but greatly reduced the damage.

In that series of tests we did about 90 roll-in arrestments at different weights, speeds, and off-center distances. Thats where the -1 arrestment limits come from. I was the General Dynamics structures engineer on the tests. Great fun, a few tense moments, lots of good stories.
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Unread post02 May 2008, 20:59

outlaw162 wrote:The whole stopping/planning process changed somewhat x-country at Buckley. Always had the hook though.


:lmao: I concur ... I guess the altitude has alot to do with lift?
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outlaw162

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Unread post02 May 2008, 23:43

Landing fast fighters: high density altitudes=higher true airspeeds=faster fighters.

Whoa, big jet!

regards
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ronholph

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Unread post28 Sep 2019, 05:07

Any of you guys encountered swerving after applying even braking pedal depression? If so what are the techniques to counter such tendencies? Is it a normal occurrence with uneven braking pedal depression when stopping the aircraft? If it's a mechanical defect, is it reflected on the 781?
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