USMCFLYR

This is for any EMB145 aircrews out there - or anyone else who knows the answer of course

I was flying on a ExpressJet EMB145 yesterday coming into ONT when I felt the configuration change but I didn't think it would have been flaps or gear based on where we were in the approach. I looked out the window behind me and saw what looked like two small spoiler like devices raised up on the top and inboard of the trailing edge flap. Later - once I knew that the Captain had lower flaps and eventually the gear, I looked again and these devices were down.

Were these devices a form of speedbrakes or some other type of high drag device to help increase the rate of descent while keeping the airspeed under control?

USMCFLYR

rickair7777

They are spoilers, designed to dump lift by goofing the airflow over that section of the wing. Spoilers generally don't work too well as speedbrakes. Of course there's the always the speed/alt energy link, but spoliers are better for increasing the descent rate...get down in a hurry, level off, THEN you can slow if needed.

Speedbrakes are more drag oriented, and for a heavy turbojet they need to be very large to do much. I think fighters can use speedbrakes due the whole drag = speed^2 thing.

SmoothOnTop

The only other two drag devices I can think of are the RR engines...

Superpilot92

Coming over the mountains there they usually leave you very high then dump you in, almost every time you will need to use the spoilers to get down and stay below 250kts. Sometimes i miss that flying. How was the ride? They treat you right?

__________________
NWA

USMCFLYR

SuperPilot92 -

"They treat you right?"

See my posts in the regional forum about my first flight experience with ExpressJet.
Short answer is BETTER THAN ALRIGHT.
Actually enjoyed it - and that says something in today's market.

USMCFLYR

USMCFLYR

Rickair -

Thanks - that is what I thought. I just haven't really noticed such devices on other RJs or such.

USMCFLYR

dojetdriver

Their primary function is shake the aircraft, provide an uncomfortable pitch change (unless we take measures to counter it), make a lot of noise, and wake the passengers up to let them know we are about to land.

The secondary function is speed brakes. We are able to use them at ANY speed in the aircraft, they have no limitation as far as speed goes. They work best at high speeds, not so great when slow. Often times when going into ONT, it's a slam dunk, and most times a come down-slow down. It's not like we get to blaze into the pattern at 300, perform an overhead and break midfield, throw it into a high G turn to dissipate speed and energy, then throw everything out on the downwind. The XR (with winglets) would probably look pretty good in the break though, the LR, eh, not so much. It's definitely a drag management exercise going into ONT sometimes. They can only be used at the first setting of flaps, but not at the 2nd, 3rd, or 4th. So as soon as more then the first flap setting is selected, they will come in. If we forget to stow them, the plane will even tell us "hey dummy, put the brakes in" in the form of a ding and a message on the EICAS.

So yep, thats what it was.

The CRJ has them also. While JS'iing, I've often seen crews use them on the 73 and 75 frequently, not so much on the airbus. But it's cool on that plane, the FMS will tell you "drag required" or something like that when you should put them out. They shake the crap out of a 75 as well.


The lever says "SPEED BRAKE" on it.

Scooter2525

haha... I like the way you said that. mind if I borrow "goofing"

SmoothOnTop

That is flipping funny, good stuff, hee hee...

rickair7777

Probably to avoid confusing RJ pilots who may not understand aerodynamic principles.

Technically speaking, spoilers extend up from the top (lift producing) surface of the wing. Speed Brakes extend from some other part of the wing or aircraft (ie fuselage, wing trailing edge, etc.)

You can also design speed brakes to deploy from the top of the wing if that's convenient for the engineer, but they don't look like the spoilers on airliners.

Obviously any drag device will have a braking effect, so a spoiler also has at least some speed brake characteristics.

However, if you look at the small size of those spoilers it should be apparaent that they don't add much direct drag to the equation...especially compared to the weight and size of any airliner. What they can do is significantly reduce lift, which then necessitates an increase in AOA to maintain Alt (or VS). Higher AOA = more induced drag. So you get the drag reduction, but in a round-about way...not from that tiny piece of metal in the slipstream, but from induced drag.