tail spoilers

[triple7]

So i was jogging down by dca this afternoon and watched a BAE(similar to the dornier jet but with 4 engines) land.....it was a nw express jet. Anyways, when it crossed the threshold and still in the air two spoilers similar to wing spoilers came out horrizonatally from the tail cone. anyone know what that is all about? seemed kinda weird.

also, on a funnier note an ERJ 145(chatauqua i think) came in and on short final to rwy19 i could see the FO's head in the window waving frantically to someone in the parking lot. i had to laugh. oh yeah, and a nw airbus had a stuck mike and for about 30 seconds you could hear him doing his final checks before taking the runway. "ok, lets wait on the packs.....lights, tranponder, blah blah blah, still waiting on the packs" an air canada crj circled to rwy 22 and did so rather dramitacally and nw airbus was heard saying, "oh wow....that looks like fun. " it was a comical way to cool down from my run.

[PanJet]

I don't know a lot about BAE jets, but if it's what it sounds like than they aren't technically spoilers because they don't destroy lift. (Somebody correct me if I'm wrong). Instead they are mainly just air brakes. I believe some of the Fokker jets (F70, F100) have something similar where the tail actually splits open and acts as air brakes. A true spoiler is found on top of the wing and the main purpose is to destroy lift by disruping the airflow over the top of the wing, although they also serve a dual purpose as air brakes.

[EatSleepFly]

[ QUOTE ]
A true spoiler is found on top of the wing and the main purpose is to destroy lift by disruping the airflow over the top of the wing, although they also serve a dual purpose as air brakes.

[/ QUOTE ]

Spoilers are also used on many airplanes to increase lateral (roll) control at low airspeeds. The Caravan has them above the outboard ends of the flaps. When an aileron deflects more than 5 deg. up (i.e.- low airspeeds), the spoiler on that side deploys proportionally to the aileron travel and disrupts airflown over that flap. The ATR has a similar system.

[mtsu_av8er]

On the MU2, it's the ONLY way to roll!!

[EricPalmer]

[holiday_inn_express_science_explaination]Also the BAE 4 engine thingy doesn't have reversers on the engines so I guess that is part of the reason for the extending tail boards. [/holiday_inn_express_science_explaination]

[Dave_Hall]

aren't spoilers that are also used for roll control known as "spoilerons".

[Doug Taylor]

[ QUOTE ]
aren't spoilers that are also used for roll control known as "spoilerons".

[/ QUOTE ]

Not necessarily! All depends on what the engineers want to call tem.

[Screaming_Emu]

[ QUOTE ]
[ QUOTE ]
aren't spoilers that are also used for roll control known as "spoilerons".

[/ QUOTE ]

Not necessarily! All depends on what the engineers want to call tem.

[/ QUOTE ]

much like the "lift detectors" on the seminole? Yet both the other pipers I've flown they're called stall warning horns. Other than having 2 of them I dont see a difference.

[blimpguy]

Roll spoilers are usually used on higher performance airplanes because they do not create adverse yaw as ailerons do. The downward-deflected aileron creates additional induced drag as it raises that wing, introducing a yawing force that tends to turn the airplane opposite the direction the pilot intended. By rolling the airplane by destroying lift and creating drag on the wing that is to be lowered, the turn can be made more coordinated without throwing more control surfaces into the relative wind creating more drag (rudder deflections).

Incidentally, we had no wheel brakes, reverse thrust, or vectored thrust on my blimp. Instead, we used full rudder deflections as airbrakes and also to fly an S-turn ground roll increasing ground friction to slow. I may not know anything about rolls, but I knows my yaws.

[ananoman]

[ QUOTE ]
On the MU2, it's the ONLY way to roll!!

[/ QUOTE ] The same goes for the Beechjet (once the MU-300), it has what looks like ailerons on the ends of the wings, but they are just trim tabs.

[Bigey]

Do you have around the time you were there?

I'd like to hear it on ATC.

[flyover]

I've seen that too. I'm sure someone will give us the real scoop but I have a pretty good idea why they deploy the brakes in flight.

Four engine airplanes carry a lot of thrust at idle. Some times it is a challenge to be at bug speed and still have the engines spooled for a go-around. It sure was the case with the DC-8.

I would assume there is some throttle logic that stows the brakes if throttles are pushed up to a certain point.

[triple7]

[ QUOTE ]
Do you have around the time you were there?

I'd like to hear it on ATC.

[/ QUOTE ]

It was around 515 or so

[Minima-No-Contact]

I fly the BAe 146, what your are referring to is purely an Airbrake. We usually get that out at about 100' above the deck. The 146 has no reverse thrust so it certainly helps with a bit of extra drag on shorter runways.

[triple7]

is there something that automatically stows that in the event of a goaround?

[flyover]

[ QUOTE ]
I fly the BAe 146, what your are referring to is purely an Airbrake. We usually get that out at about 100' above the deck. The 146 has no reverse thrust so it certainly helps with a bit of extra drag on shorter runways.

[/ QUOTE ]

The obvious question for those of us that don't fly it is, why 100' AGL? Seems like that would be a bad place as far as a stabilized approach. Inquiring minds want to know.

[Snow]

Space shuttle has one of those too.

[EatSleepFly]

[ QUOTE ]

The obvious question for those of us that don't fly it is, why 100' AGL? Seems like that would be a bad place as far as a stabilized approach. Inquiring minds want to know.

[/ QUOTE ]

I don't know the answer, but "stabilized" and "fully-configured" aren't necessarily the same thing.

At least not in my world!

[Maximillian_Jenius]

[ QUOTE ]
[ QUOTE ]
Do you have around the time you were there?

I'd like to hear it on ATC.

[/ QUOTE ]

It was around 515 or so

[/ QUOTE ]


Whaaaaaa...you were able to dicipher his crap language skills???

-Matthew

[Minima-No-Contact]

Hey guys,
Good questions.
I've only been flying the 146 for 2 months now, and I had the same sort of thoughts initially.

The airbrake gets deployed at about 100' because it's required to be out for landing - a performance requirement in calculating landing distance and every bit of drag helps on those shorter runways. If you get the airbrake out above 100' you find yourself adding a little bit too much power to keep your speed on, when you should be slowly getting the power off.

The airbrake causes a very slight pitch up. Not enough to de-stablize an approach. Its just one of those things you get used to. Hands going everywhere at 100' wasn't much fun initially, but like most things in aviation, it becomes second nature very quickly.

The airbrake will not stow automatically during a missed approach. The standard call when you initiate the missed, is "Flap 24, airbrake in" - it all happens very quickly and isn't a problem.

The 146 is very old english technology, but even now it does a great job and they tell me it is a relatively cheap aircraft to operate.