Anti-Skid

[Guest mfont]

This past weekend I got a chance to go to Eglin AFB on a base visit for ROTC. We toured one of the facilities which I believe was a training center for Eagle crew chiefs. Inside of this building was a mock cockpit of an F-15 and one of the NCOs started explaining some of the features. She told us how one feature exclusive to Eagles was "Anti-Skid," which apparently is a switch in the cockpit that a pilot can operatate, and when activated, he/she can fly in totally coordinated flight without using the rudders (on-board computers operate the rudders automatically.) Can any pilots on this board explain this feature in greater detail? What phases of flight is it used in? Must all Eagle drivers utilize this feature or do some prefer to fly the "old fashioned" way? I know that there are some times when a pilot needs total control over his/her rudders, but the crew chief told me that all pilots use this feature 100% of the time--is this true? Thanks in advance for any replies.

[Guest eaglekeeper]

Anti-skid is an automatic braking system used in wet or slippery runway conditions. The systems kicks in when the MLG tires go off center. The sensor is located on the bottom of the gear. The flight control system you are refering to is CAS, and the system is used throuhout the entire flight. The Aileron Rudder Interconnect(ARI)is the computer that links the two flight controls. Unlike the fly-by-wire systems on the viper, the eagle uses mechanical links.

[Guest JArcher00]

Ever hear of a yaw-damper.

[Guest lovelacm]

On an E-Model Herk, a "Yaw-Damper" = the pilot's legs.

Often heard on a copilot's first Pilot Proficiency rides at Little Rock, "Come'on, Co... lead with a little more rudder.. center the ball..."

Oh, that's right... no more copilots in the pipeline.. just the MPD folks. Anybody got a line on how that's playing out in the operational squadrons?

[Guest rumblefish_2]

The Viper's computer (Hal) inputs the rudder needed to keep coordinated flight. It's almost never that a Viper driver should even need to use the rudder because of the fly-by wire system. The jets are often bent however, so a little rudder trim is usually needed to initially center the ball. Split slabs are pretty cool, too. Hal also trims the jet to try and maintain 1G flight. Now if Hal would just let me land the airplane and not try to keep me flying in the flare...

The anti-skid switch should be a braking feature like eaglekeeper said.

[BONE Co-driver]

Same for the B-1. We actually have 2 rudders. Under normal flight the computer controls the lower rudder for coordinated flight. The only time that I have seen us even touch the rudder is for taxi ops, engine out flight/approaches, and crosswind landings. Other than that, our feet are flat on the floor.

[BlackJetDriver]

B-2 has no rudder (go figure). The jet uses differential spoilers, elevons and the "beaver tail" to maintain lateral control. Feet flat on the floor almost 100% of the time. HAL takes care of it all.

[HerkDerka]

Linda

All I know about the MPD is that all true copiglets were suddenly upgraded to FPs by ARMS. Why? I don't know. I even asked ARMS and they don't know. I think it's just making way for the future.

Back on topic. In the Herk, you may only have one rudder (barn door) but you have two pessure settings. High rudder boost and low rudder boost depending on the setting of the flap lever. Gives you that extra control at low airspeed which is ever so essential in an aircraft with four Hamilton Standards.

HD

[Guest ViperDriver98]

That sounds like something someone would say right after "hand me that bucket of prop wash". In the Viper anti-skid is all about the braking. The F-16 switch has 3 positions: Parking Brake, Anti-Skid (which it is in most of the time unless we use the parking brake) and Off. The off option is for anti-skid malfunctions, so it's rarely turned off.

Hal does a lot of the work for us in trimming but like rumblefish said we need to trim it out using our trim knobs, and mostly just rudder trim. If you use the auto pilot, however, it takes out all of the trim inputs. There are plenty of times when we fly BFM (basic fighter maneuvers) want to demand more from the jet than it will give us, but the limiters are there to keep us from putting the jet out of control.

But maybe it's different in the eagle.....

[ 10. May 2005, 03:26: Message edited by: ViperDriver98 ]

[Toro]

Originally posted by ViperDriver98:

The F-16 switch has 3 positions: Parking Brake, Anti-Skid (which it is in most of the time unless we use the parking brake) and Off. The off option is for anti-skid malfunctions, so it's rarely turned off.

Is it possible to unintentionally go from anti-skid to parking brake in the case of a brake emergency? Seems like bit of an accident waiting to happen (our parking brake is on the other side of the cockpit) Rolling out on landing with no brakes, I could see somebody with a braking problem trying to switch the thing to off and taking it to parking brake (guarded switch)? 69 knots to stopped in 1/2 second with a couple blown tires.

In the Strike Eagle the brake switch has Anti-Skid, Pulser, and Off. The switch normally sits in Anti-Ski. In a loss of brakes we first go to Pulser, which applies brake pressure in a pulsing motion. It'll get the jet slowed down to a fast taxi speed, but then the switch needs to be thrown to off to continue stopping with normal (no anti-skid) braking.

As far as trim goes, I hardly ever touch the rudder trim knob. The auto pilot will keep us level regardless of trim inputs. We have no limiters like the Viper.

[Guest HueyPilot]

Well, the Herk is covered here...so I'll spin off some C-21 trivia...

Anti-skid and rudder/aileron coordination isn't something that's exclusive to Eagle pilots, as the above posts show.

The C-21 has both...anti-skid on the C-21 is similar to a car's anti-lock braking system. There are sensors in each wheel that measure rotation, and when they don't match (due to one or more wheels locking up), hydraulic pressure is vented to release the brakes and keep the brakes from locking up. If you stomp on the brakes hard enough in the C-21, you can feel the rudder pedals pulsating...that's the pressure being vented to keep the wheels all turning the same speed.

As for aileron/rudder interconnect, the C-21 has a mechanical system that keeps the airplane coordinated in turns. If you ever sit in a C-21 cockpit, center the yoke and push the rudder pedals full deflection...after a few degrees of travel, you'll see the yoke move a bit...that's the interconnect working. That combined with a dual yaw damper system makes the C-21 a feet-on-the-floor jet as well...unless you're flying single-engine.

[Guest SnakeT38]

I forgot all the nums on anti-skid for A-10, B-52,

T-38 (hah hah), 727, DC-10/10/30, F100, MD-11,

however I do retain minor knowledge of said system on my current A/C the MD-80........

[Guest HueyPilot]

F100....did you fly for AA?

[Guest SnakeT38]

Originally posted by HueyPilot:

F100....did you fly for AA?

I do..........at least I am on the "trip" tomorrow.

[Guest HueyPilot]

Do you know Dave Bailey? I flew with him in the LAARNG for a while. He's a Brit, kinda quirky personality.

[Guest SnakeT38]

Originally posted by HueyPilot:

Do you know Dave Bailey? I flew with him in the LAARNG for a while. He's a Brit, kinda quirky personality.

DFW based??? Heard the name, can't place the face.

[Guest HueyPilot]

yeah, I think he's DFW based...got hurt in a UH-60 crash in Iraq though. So I don't know if he'll be flying again. I think he was on F100s if I remember...but that was a few years ago.

[Bergman]

Originally posted by SnakeT38:

I do..........at least I am on the "trip" tomorrow.

[Guest SnakeT38]

I didn't "miss it" by far! However, I do

REMEMBER sitting in my 4th grade class at Clark AFB in the early stages of Vietnam and "feeling"

4 ships of 105's takeoff for the "Nam". There was always at least one "earthquake" per day!

Our neighbors for awhile, none other than Chuck Yeager.

[Guest ViperDriver98]

Originally posted by Toro:

Is it possible to unintentionally go from anti-skid to parking brake in the case of a brake emergency? Seems like bit of an accident waiting to happen (our parking brake is on the other side of the cockpit) Rolling out on landing with no brakes, I could see somebody with a braking problem trying to switch the thing to off and taking it to parking brake (guarded switch)? 69 knots to stopped in 1/2 second with a couple blown tires.

Stranger things have happened and I suppose that it is possible to screw it up that way, but I've never heard of it happening. The switch is one of the ones with the three detents that you have to pull out to move from one position to another so you can't bump it. The Parking Brake is in the up position, Anti-Skid is centered, and off is down. The OFF only turns the Anti-Skid off, not the brakes all together. You can use the parking brake to stop the aircraft if you need to (at taxi speeds). You could blow tires if you are too aggressive stopping when you have the anti-skid off.

[Guest SnakeT38]

Originally posted by ViperDriver98:

You could blow tires if you are too aggressive stopping when you have the anti-skid off.

[Guest Hoser]

As far as trim goes, I hardly ever touch the rudder trim knob.

We have rudder trim????

We have no limiters like the Viper.

You forgot about the rudder limiter, you know, the WSO's feet as he uses the rudder pedals for foot rests!

Hoser

[ 11. May 2005, 22:54: Message edited by: Hoser ]