Maximum Brake Speed

[peanuthead]

Hello

The real F-16 take-off and landing data (TOLD) cards have a line for max brake speed. The Brake Energy Limits chart (Page 190 of the Dash 1) shows that braking above 160 knots (at max takeoff weight) would exceed 24.5 million foot pounds and cause gear failure. The rotation speed at maximum takeoff weight (48,000 Lbs) is around 195 knots. Does this mean we cannot apply brakes past 160 knots assuming I read the chart correctly? The max brake speed contradicts the abort procedure which says throttle idle, speedbrake open, maximum effort braking; nothing about obeying the max brake speed.

Thank you

[Red Dog]

Aborting can’t be done without some considerations:

• Speed, committed to take off
• Runway remaining, runway conditions (not implemented in BMS)
• Barrier available (not implemented in BMS)
• Weather, Visibility
• Antiskid (not implemented in BMS)

First, let me ask you this: How many take off abort did you do in Falcon: Me in 20 years: none. There was never a reason to do it

Second, once you’re committed to takeoff (past a certain speed) it’s often better to go flying and deal with the emergency once in flight.
The limit of the brake is one of these conditions that may lead to actually go flying and make an emergency landing, where your speed (and the runway in front of you) will be more forgiving
of course if you lost your engine, you can’t really go flying. In those rare case of engine failure between 160 and 190 kts at full GW, then I’d say the jet betrayed you so try anyway and hope you have these big wing bags when the gear collapse either because of the brake effort or because they meet the grass (which doens’t happen in BMS either ) And if all else fail - You still have that yellow handle though

If you have enough runway and decide to abort, the official abort procedure says:

Aborts above 100 KCAS require diligent adherence to the procedures in this section for the abort to be successful. If aborting after rotation, retard throttle to IDLE and maintain two point attitude while applying maximum wheel braking (maximum pedal pressure (antiskid on) consistent with maintaining directional control). When wheel brakes become effective, the nose automatically lowers. After the nosewheel is on the runway, use maximum effort braking (full aft stick, full open speedbrakes, and maximum wheel braking). If aborting before rotation, retard throttle to IDLE, maintain threepoint attitude and apply maximum effort braking if stopping distance is critical. NWS should be engaged if directional control is a problem.

So you don’t use max effort braking right from the start of the abort, you first place the nosewheel on the ground then apply max effort braking.
Chances are that when the nosewheel is on the runway you’ll be under 160… if not I guess you took the wrong decision (and the runway end might be very close)

[Frederf]

The fact that the procedure doesn’t specifically address brake energy limits doesn’t contradict that limit. Maximum effort braking may mean no brakes applied if some brake energy limit is to be obeyed. The refusal speed chart note bullet points include the assumption of no braking above max application speed. In short, yes you will delay applying brakes to comply with other limits. It’s built into the word “maximum” meaning “most you are allowed to do.”

[Radium]

Hello,

Manuals should be checked ; for example :

From : NATO + FAA :

V1 is the critical engine failure recognition speed or takeoff decision speed. It is the speed above which the takeoff will continue even if an engine fails or another problem occurs, such as a blown tire. The speed will vary among aircraft types and varies according to factors such as aircraft weight, runway length, wing flap setting, engine thrust used and runway surface contamination, thus it must be determined by the pilot before takeoff.

From AFI11-2F-16V3 :

On training missions, not takeoff if the computed takeoff roll exceeds 80 percent of the available runway single ship or 70 percent for a formation takeoff

Cheers,

Radium

[Dee-Jay]

@peanuthead:

Hello

The real F-16 take-off and landing data (TOLD) cards have a line for max brake speed. The Brake Energy Limits chart (Page 190 of the Dash 1) shows that braking above 160 knots (at max takeoff weight) would exceed 24.5 million foot pounds and cause gear failure. The rotation speed at maximum takeoff weight (48,000 Lbs) is around 195 knots. Does this mean we cannot apply brakes past 160 knots assuming I read the chart correctly? The max brake speed contradicts the abort procedure which says throttle idle, speedbrake open, maximum effort braking; nothing about obeying the max brake speed.

Thank you

Do not confuse normal ops and emergency. An aborted take-off is an emergency case at and brakes are used beyond max nominal energy capabilites. After an aborted takeoff at max speed, brakes blocks are tosted.

[Blu3wolf]

You get the fun of waiting in the hot brakes bay for the tyre plugs to melt, I guess…

[Frederf]

@Dee-Jay:

Do not confuse normal ops and emergency. An aborted take-off is an emergency case at and brakes are used beyond max nominal energy capabilites. After an aborted takeoff at max speed, brakes blocks are tosted.

If runway is long enough and TOLD calculations say it can be done obeying the limit there is no reason to cook the brakes. If max speed abort + coast to max brake apply speed is allowable within runway length there is no reason to cause a brake fire.

[nove]

@Dee-Jay:

Do not confuse normal ops and emergency. An aborted take-off is an emergency case at and brakes are used beyond max nominal energy capabilites. After an aborted takeoff at max speed, brakes blocks are tosted.

[Kukailimoku]

@Dee-Jay:

Do not confuse normal ops and emergency. An aborted take-off is an emergency case at and brakes are used beyond max nominal energy capabilites. After an aborted takeoff at max speed, brakes blocks are tosted.

Many accounts have been written about B-52 emergencies and near-emergencies. Those are very heavy, especially when had to return soon after take-off or come down to a different field that maybe wasn’t as long a runway as ideal or nominal. In cases where fire didn’t actually break out (pun!) the fire trucks standby over the hot wheels for a long time / they hose it / they put ventilation fans on the hot wheels (pun again).

I think the aborted take-off emergency trumps the normal ops’ constraints of overheating the brakes.
Related: IDK if small military planes have similar, but large airliners have a few v-speeds governing take-off. V1 is the speed at which you CANNOT abort (because not enough time/distance remains to stop without rolling off the end of the runway), V2 is the minimum for climbing with one engine dead, etc. We probably don’t have V2 in BMS…

[Kukailimoku]

@nove:

https://i.postimg.cc/26GwmchY/2018-11-25-145927.png

Whose the baton babe? Air farce chicks always looked better than Army chicks.

[Blu3wolf]

@Kukailimoku:

Many accounts have been written about B-52 emergencies and near-emergencies. Those are very heavy, especially when had to return soon after take-off or come down to a different field that maybe wasn’t as long a runway as ideal or nominal. In cases where fire didn’t actually break out (pun!) the fire trucks standby over the hot wheels for a long time / they hose it / they put ventilation fans on the hot wheels (pun again).

I think the aborted take-off emergency trumps the normal ops’ constraints of overheating the brakes.
Related: IDK if small military planes have similar, but large airliners have a few v-speeds governing take-off. V1 is the speed at which you CANNOT abort (because not enough time/distance remains to stop without rolling off the end of the runway), V2 is the minimum for climbing with one engine dead, etc. We probably don’t have V2 in BMS…

You can calculate V1 if you like. V2 you will definitely run into some issues I imagine.

WDP will calculate a max abort speed for you automatically. You can do it manually using the charts in a real performance manual if you want (F-16CX-1-1), but WDP is pretty convenient. Obviously, emergencies below takeoff speed, you perform an abort. An abort is a CAPS item, so you should have it committed to memory. For emergencies above takeoff speed, you should be in the air, so they are takeoff emergencies - which are also CAPS items. Committed to memory. Light twins up to airliners, the sequence seems to be V1, rotate, V2 (take with a grain of salt, Ive never flown either type), so between V1 and V2 if you have an engine failure you are just stuffed. The F-16 has pretty enviable performance though, so for us it tends to be that we get airborne well before reaching our abort speed. Obviously we are just as stuffed with an engine failure though!

Its also generally an option to do an AB takeoff, if the MIL takeoff would start to run into the abort speed before reaching takeoff speed. So given that, as long as we plan our takeoff, that makes our emergency management in the takeoff phase really simple. Before takeoff, we perform an abort - throttle idle, hook down if you like (without arresters, its just eye candy), brakes as required. After takeoff, for an engine failure we zoom, stores jettison, and eject.