DC 9 question
 

Can a DC 9 be pushed off the gate or does it always have to do a power back?

ORP? :confused:

Good discussion at airliners.net
http://www.airliners.net/discussions....main/2639112/

(found it by googling dc-9 power back)

Was on a NW DC-9 with power back a few weeks ago at DTW. I thought it was odd as I thought they stopped it due to extra fuel burn ($$$$). It could have been because we were running a little late and they didn't want to wait for a push.

Pushes seem much more common.

This is standard practice at DTW. It is because though it takes more fuel, it means they do not have to have as many (expensive) push vehicles as they would otherwise.

Did this at MEM last Saturday on a DC9-50.

Whenever I fly a DC 9 out of DTW, we always self pushback. Has been that way for a couple years.

Great pointer to the Airliners.net thread, but it raised another question.

It said that they do it mostly with tail-engined aircraft because of the risk of sucking in Foreign Object Damage (FOD) junk with below-main-wing engines.

Is there extra FOD risk during reverse thrust? Or is it just that pushback or powerback happens close in to the terminal/bridge, where there's more likely to be junk? Underwing-engined jets taxi in that area when they come in. What's the difference?

It can do either.

AA used to power back their MD-80s (DC-9-80s) fairly frequently. But there are dangers to backing up without the use of a rear-view mirror, in addition to the possibility of sucking debris into an engine.

FOD is Foreign Object Debris, although it could become damage. ;)

As far as I know, the reason is that most FOD is near the terminal, not on the runway. While jets do taxi in that area, the engine setting is much less than it is for reverse thrust. Engines are not really designed to go backwards, which is why you hear WHOOOOOAAAAR during a powerback just to move a couple of MPH (and thus the wasted fuel).

It isn't terribly dangerous, because you use wing spotters (don't know what they are called). One on each wing, with those little things they wave around.

I was on a flight where the captain came on and told us we would have to wait for a tug because the gate we were at was in a confined area and powerbacks weren't allowed from that particular gate. That was years ago, so I don't remember the airline/airport/plane type details.

It's called a power-back as apposed to a push-back. The DC9 can do either.

In order to do power-backs the airline must have authorization for power-back operations in their FAA operation specifications (OpSpecs). The OpSpecs will list the exact airports and gates at which a particular type airplane is authorized for power-back operations. Not all gates at all airports will be authorized.

Wing walkers are used and a marshaller gives the Captain hand signals during the power-back. It starts out with powering forward a few feet to get the airplane moving. Once the airplane starts rolling forward the reversers are engaged and the airplane powers-back. The Captain keeps his feet on the floor during the power-back as you can't apply brakes while backing up as doing so could cause the plane to tip back onto it's tail. To stop the power-back the reversers are stowed and forward thrust is used to stop the airplane.

All airplanes are more prone to FOD when in reverse at slow speeds. The reversers work by redirecting the exhaust somewhat forward but a lot of the exhaust goes up, down and to the sides as well. This will kick up any debris on the ground and could easily be ingested into the engine. During landing, the airplane is moving fast enough that the airplane is well down the runway by the time any debris would reach the engine's height but you do generally stow the reversers by 60 knots, or so, to reduce the chance of FOD ingestion at slower speeds--this is especially true with under-wing mounted engines.

Not all airlines have authorization for power-backs so while you see them frequently on AAL MD80s there will be other MD80/DC9 operators who never use them.

Either term is acceptable, but I believe Foreign Object Damage is much more widely used, especially in the military aviation context. Here's one link out of many. During my flying days in the Navy we always referred to it that way. Even when we did our end to end carrier flight deck FOD walkdowns to pick-up stray bolts or safety wire, we didn't redefine the acronym. I guess it was just a colloquialism that extended to mean both the item and damage.

Debris is accurate. Those ramp folk don't go around picking up f.o.damage - they go around picking up f.o.debris