F-15 speed brake

[signals]

I'm making a F-15I from the academy kit and was wondering if someone could give me an idea of how far to open up the speed brake. The model is in-flight - hence the gears up and the intakes drooped....

Any real images of an Eagle with the break opened mid-flight would be cool to see as well

[Jennings]

Gear up and intakes drooped with the air brake open would be nearly impossible to see in real life. If the gear is up, the airplane is going fast enough that the intakes would also be up. I suppose the speed brake could be out, but only momentarily (it's *very* effective). As for how far it goes up, does the model have a hydraulic ram for the brake? If so, measure the length of the long section of the cylinder, then roughly double it for the maximum extended length of the piston. Put that in position under the brake and you'll see how far it can extend upward. From memory (distant) I believe it's in the neighborhood of 60 degrees from the closed position, but don't quote me on that.

[gary1701]

Hi,

This is the best I can find that I've got with the brake full distance. They're usually being retracted when I shoot them over the approach at Lakenheath. I couldn't find one pic with the wheels up and the brake out and I can't say I've ever seen it.

Over the fence. by Garysted, on Flickr

Gary

[Ol Crew Dog]

I'm making a F-15I from the academy kit and was wondering if someone could give me an idea of how far to open up the speed brake. The model is in-flight - hence the gears up and the intakes drooped....

Any real images of an Eagle with the break opened mid-flight would be cool to see as well

There is only 2 positions on the speedbrake, fully extended and fully retracted, nothing inbetween.....

Gear retracted as in in flight the ramps are constantly move ing to account for air speed and AOA to maintain maximum efficient airflow across the engine...

The switch in the cockpit for the vari ramps has 2 positions emerg which puts them full up an auto which puts them full down on the ground but they move in flight.

Any failure I the vari ramp system will cause them to go to emerg position, on ground to prevent FOD ingestion while taxiing and engine maintenance runs set to emerg....

Speed brake can be open in flight but as has been said is very effective so about 210 mph it does not open IIRC.....

Cheers

Dave

[Ol Crew Dog]

Hi,

This is the best I can find that I've got with the brake full distance. They're usually being retracted when I shoot them over the approach at Lakenheath. I couldn't find one pic with the wheels up and the brake out and I can't say I've ever seen it.

Over the fence. by Garysted, on Flickr

Gary

Thus on approach, never on take off and high speed flight.....

[Waco]

There is only 2 positions on the speedbrake, fully extended and fully retracted, nothing inbetween.....

Sorry, but that's not true. The switch is a 3 position switch: extend-hold-retract. When flying on the wing during close formation, particularly during a formation approach (configured with gear down, flaps extended), it was normal procedure to partially extend the speed brake a small amount. This allowed the wingman to maintain a slightly higher power setting, allowing for faster response time on the engines as required. The speedbrake can be deployed and held at any intermediate position between full open and full closed.

It's true the brake will not extend above certain airspeeds, and the aircraft will automatically limit its maximum open position based on current conditions as necessary. I don't remember the airspeed at which it is prevented from opening, and I no longer have a copy of the F-15A-1, so I can't look it up. However, it will deploy at speeds significantly higher than 210KIAS. In early models of the Eagle, before the installation of the chaff-flare dispensing system, crew chiefs used to load chaff bundles under the speed brake for one-time use during missions. You'd be at MUCH higher speeds to open and deploy the chaff in that configuration. Also, from talking to guys who flew the jet back in the early days, the speedbrake was routinely deployed to control closure during BFM/1v1 engagements. However, this was subsequently written in as a prohibited procedure, as an open SB will cause the jet to go out of control above a certain angle of attack. Although the SB will automatically retract prior to reaching this AoA, a sudden onset rate of alpha could cause temporary conditions exceeding this higher AoA, and a sudden, rapid departure from controlled flight.

It IS an extremely effective tool for slowing the aircraft down. Not nearly as effective as the F-22's asymmetrical deployment of flight controls when speed brake is selected, but it'll still slow the Eagle down pretty quickly.

[Ol Crew Dog]

Sorry, but that's not true. The switch is a 3 position switch: extend-hold-retract. When flying on the wing during close formation, particularly during a formation approach (configured with gear down, flaps extended), it was normal procedure to partially extend the speed brake a small amount. This allowed the wingman to maintain a slightly higher power setting, allowing for faster response time on the engines as required. The speedbrake can be deployed and held at any intermediate position between full open and full closed.

It's true the brake will not extend above certain airspeeds, and the aircraft will automatically limit its maximum open position based on current conditions as necessary. I don't remember the airspeed at which it is prevented from opening, and I no longer have a copy of the F-15A-1, so I can't look it up. However, it will deploy at speeds significantly higher than 210KIAS. In early models of the Eagle, before the installation of the chaff-flare dispensing system, crew chiefs used to load chaff bundles under the speed brake for one-time use during missions. You'd be at MUCH higher speeds to open and deploy the chaff in that configuration. Also, from talking to guys who flew the jet back in the early days, the speedbrake was routinely deployed to control closure during BFM/1v1 engagements. However, this was subsequently written in as a prohibited procedure, as an open SB will cause the jet to go out of control above a certain angle of attack. Although the SB will automatically retract prior to reaching this AoA, a sudden onset rate of alpha could cause temporary conditions exceeding this higher AoA, and a sudden, rapid departure from controlled flight.

It IS an extremely effective tool for slowing the aircraft down. Not nearly as effective as the F-22's asymmetrical deployment of flight controls when speed brake is selected, but it'll still slow the Eagle down pretty quickly.

Thank you for the clarification Waco, been Agee years...

[Ol Crew Dog]

Sorry, but that's not true. The switch is a 3 position switch: extend-hold-retract. When flying on the wing during close formation, particularly during a formation approach (configured with gear down, flaps extended), it was normal procedure to partially extend the speed brake a small amount. This allowed the wingman to maintain a slightly higher power setting, allowing for faster response time on the engines as required. The speedbrake can be deployed and held at any intermediate position between full open and full closed.

It's true the brake will not extend above certain airspeeds, and the aircraft will automatically limit its maximum open position based on current conditions as necessary. I don't remember the airspeed at which it is prevented from opening, and I no longer have a copy of the F-15A-1, so I can't look it up. However, it will deploy at speeds significantly higher than 210KIAS. In early models of the Eagle, before the installation of the chaff-flare dispensing system, crew chiefs used to load chaff bundles under the speed brake for one-time use during missions. You'd be at MUCH higher speeds to open and deploy the chaff in that configuration. Also, from talking to guys who flew the jet back in the early days, the speedbrake was routinely deployed to control closure during BFM/1v1 engagements. However, this was subsequently written in as a prohibited procedure, as an open SB will cause the jet to go out of control above a certain angle of attack. Although the SB will automatically retract prior to reaching this AoA, a sudden onset rate of alpha could cause temporary conditions exceeding this higher AoA, and a sudden, rapid departure from controlled flight.

It IS an extremely effective tool for slowing the aircraft down. Not nearly as effective as the F-22's asymmetrical deployment of flight controls when speed brake is selected, but it'll still slow the Eagle down pretty quickly.

I remember the days of stuffing chaff bundles under the speedbrake and reminding the pilot when he cycled the flight controls not to cycle the speedbrake.

Cheers

[Murph]

I remember the days of stuffing chaff bundles under the speedbrake and reminding the pilot when he cycled the flight controls not to cycle the speedbrake.

Cheers

On my mission check out of MQT I had the crew chief stick a couple bundles of chaff under the speed brake. As it turned out, I didn't need it during the tactical portion of the missions, so it ended up getting dumped, unintentionally, during the RTB. It wasn't infrequent that it didn't last past the rejoin on departure, depending on the wingman's closure on the flight lead.

Regards,

Murph

Edited October 27, 2013 by Murph

[BMH]

I'm making a F-15I from the academy kit and was wondering if someone could give me an idea of how far to open up the speed brake. The model is in-flight - hence the gears up and the intakes drooped....

Any real images of an Eagle with the break opened mid-flight would be cool to see as well

Here's a clip of an F-15D flying chase on one of the F-23 prototypes (great doc when you have some time)--shows the speed brake extended at nearly the angle shown in the F-15E shots above, but it's gear up and intakes closer to straight on than drooped:

Sequence is at 41:02:

http://www.youtube.com/watch?v=xGco66RoJtc

[Buck]

Hope this helps a little...

F-15E joining up on us, board on it's way up (at this point) and inlets down slightly and more or less in-line with airflow I'm guessing (and whatever else the AIC is using ;)/>/> ) Airspeed, in the neighborhood of 300KIAS (+/- the odd knot or two).

Ahui hou :cheers:/>/>

Mark

Edited October 31, 2013 by Buck

[pigsty]

To be really technical, the airbrake has an infinite range of possible positions. It may be pre-set to be fully open or not open at all, but it can't move instantaneously from one to the other, so while it's cycling it can be at any intermediate angle. Buck's picture nicely illustrates this: the airbrake is partly open on its way to one or other extreme. (Also interesting that the intakes have nodded in that picture.) So you can, in theory, depict any angle you like and it will be right, momentarily.

Can anyone explain why the airbrake has come to be known as a "speed brake"? All brakes reduce speed, it's what they're for. Calling this panel the airbrake usefully distinguishes it from the ones on the wheels and reminds you (if you need reminding) that it's the one you use while in the air.

[Buck]

Can anyone explain why the airbrake has come to be known as a "speed brake"? All brakes reduce speed, it's what they're for. Calling this panel the airbrake usefully distinguishes it from the ones on the wheels and reminds you (if you need reminding) that it's the one you use while in the air.

Howzit Pigsty,

On our jet the lever that raises & lowers all 4 spoilers simultaneously is actually labeled "Speed Brake". Pretty sure most fast-movers have similar labeling on their throttle grip, I know the Viper does... Think it's SPD BRK or something similar ;)

HTH

Mark

[Rank11]

Airbrakes are for trucks!

[ALF18]

Sounds like the Eagle's speedbrake works similarly to the Legacy Hornet's. Even if I set the switch to "extend", it would only extend as far as it could based on Calibrated Airspeed, to prevent excessive airloads on the structure and hydraulic jack. This meant that at very high speeds (say 500 kts), the speedbrake would only extend a few degrees (say about 10), while at 250 kts, it would go all the way up like a barn door. At high speeds, it was effective, but in the middle speed range where it would go out to its deflection limit, it was the most effective.

I recall one day rejoining straight ahead on another Hornet, and misjudging my closure a bit. Just as I put out my speedbrake, he put his out too, because we were high and fast on our instrument approach in clear air. I was doing 400+; he was at about 300. My speedbrake went out slightly, and his went WAY up in the air... net effect was I sailed past him and had to barrel roll around him to control closure as his jet decelerated way faster than mine, and from a slower speed.

As described above, we often called for speedbrakes to be extended in close formation, so that we would both have higher power settings and allow the wingman to finely control his position at an engine thrust range that was more variable than close to idle in a descent.

Two things:

1. There are rarely pics of in-flight speedbrake deployments, because they are momentary, used during phases of flight that are more intense than cruising, and almost never seen by a ground-based photographer.

2. The nomenclature is interesting. In England, Airbrake is the proper term. In the USA and Canada, we say Speedbrake. Just like Americans/Canucks say Afterburner, while Brits tend to say "reheat".

ALF

[Ken Middleton]

Hope this helps a little...

F-15E joining up on us, board on it's way up (at this point) and inlets down slightly and more or less in-line with airflow I'm guessing (and whatever else the AIC is using ;)/>/>/>/>/> ) Airspeed, in the neighborhood of 300KIAS (+/- the odd knot or two).

Ahui hou :cheers:/>/>/>/>/>

Mark

Fantastic photo Mark! Clearly shows all the things he is looking for

Here's a side shot of an F-15C with the speedbrake open, I zoomed in on the pic and the intakes "appear" to up. Hope it helps by being a side shot

Edited November 16, 2013 by Ken Middleton

[DonSS3]

Good stuff, Alf, thanks for sharing your experience.

[GEH737]

They might be technically "airbrakes" - but we use whatever term strikes us during the conversation (with Tactical pilots - usually involving our hands in re-creating the tale...) The technical term on the A-10 was "Decelerons" (yes we needed 'em, and no, we never called 'em that. Much like that it was never, ever referred to as the "Thunderbolt II). With the "airbrakes" - It was usually "popped the boards", or "hit the brakes". Even now on the 737, the terms most commonly used is "speedbrakes" or "boards". Using slang or acronyms is just standard speech patterns for us. With so many technical terms involving aircraft, they can often become forgotten - and in a quick conversation - a nonsensical term can be used interchangeably when describing something. It's weird, but it works.

Hitch

[Ol Crew Dog]

They might be technically "airbrakes" - but we use whatever term strikes us during the conversation (with Tactical pilots - usually involving our hands in re-creating the tale...) The technical term on the A-10 was "Decelerons" (yes we needed 'em, and no, we never called 'em that. Much like that it was never, ever referred to as the "Thunderbolt II). With the "airbrakes" - It was usually "popped the boards", or "hit the brakes". Even now on the 737, the terms most commonly used is "speedbrakes" or "boards". Using slang or acronyms is just standard speech patterns for us. With so many technical terms involving aircraft, they can often become forgotten - and in a quick conversation - a nonsensical term can be used interchangeably when describing something. It's weird, but it works.

Hitch

On the Eagle (yes we called it that on the line) all tech data and on the line we called it a "speedbrake".

I have been thinking and yes we had slang for a few things but mostly we used the technical term,

Mostly when you got Simone from F-4 's or A-10's you would hear that slang and I am sure it filtered into the Eagle world but for over 20 years of me working the Eagle we called things with the technical tem.

I do see your point about "Thunderbolt II" and the same goes with the fighting falcons (Lawn Darts).

Cheers

[GreyGhost]

Just for illustrative purposes ...

Blue Jet #7 with partially deployed speedbrake:

>>> Hi Res <<<

-Gregg