Why?

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Why?

Postby skoker » Tue May 24, 2011 2:11 pm

http://www.airliners.net/photo/USA---Ma ... 7003002f98

Why do DC-9's park with their thrust reversers open?   I see this all the time. :)
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Re: Why?

Postby Flying Trucker » Tue May 24, 2011 6:41 pm

Hi Skoker...

Wonder if it is part of the Pre-Flight Inspection?

202.1.1 Thrust Reverser
a. What is its function?
The thrust reversers direct engine exhaust gases forward, above and below the engine nacelle to reverse forward motion.
b. Where is it located?
Each engine is equipped with a thrust reverser that consists of two doors or deflectors, that form the aft nacelle fairing when
the doors are in the stowed position.
c. What are the safety precautions?
The reverser control valve has a manual override control arm that may be manually operated from the exterior of the aircraft
through an access door to deactivate the thrust reverser doors in the stowed or open position for safe ground maintenance or
inspection. To operate the manual override, the control valve arm is rotated to the dump position and a safety pin, provided in
stowage clips, is inserted through the control valve arm. This action ports thrust reverser actuator and accumulator pressure to
return, and aircraft hydraulic system pressure is blocked. [glow=yellow,2,300]The access door to the reverser control valve cannot be closed until
the override control arm is placed in a safe flight position.[/glow]
202.2 Auxiliary

http://members.cox.net/navyewarfare/files/c9EAWS.pdf

Move slider about 1 inch from bottom of page...

Not sure if that Link helps or not...

Also...

It was not uncommon for DC9s to back out of their parking area.

The reason that it's rare, of course, is that in a confined space running most planes' engines with reversers deployed would stir up a lot of dirt and grit, much of which would be sucked into their intakes. Foreign-object damage (called FOD) would quickly be the result. But some aircraft, such as DC-9s, have their engines mounted sufficiently high and sufficiently far back that FOD isn't a big risk. Some airlines routinely have some of their aircraft at some of their gates back away from the gate using reversers. That's called a "powerback" in contrast to a pushback, which a plane gets from a tug.

POWERBACK

Northwest now Delta only permits powerbacks at the three hubs that DC-9s visit - MSP, DTW, and MEM. Furthermore, there are gates at each of those airports that powerbacks are not allowed to be performed from (too small an alley, close side-by-side arrangements, etc.).

The pilots know beforehand from the ground crew if they'll be doing a powerback and they inform ramp control of this upon initial contact after receiving the clearance. When the clearance for the powerback is given the ramper in front of the cockpit gives the ready-to-go signal and puts his goggles on.

Both pilots take their feet off of the rudder pedals and put them on the floor. The captain pushes the power just enough to breakaway thrust and rolls the jet forward a few feet to get the tires off of the soft spots so that minimal reverse thrust is needed. After moving forward these couple of feet, he or she goes back to idle and thing brings both engines into reverse thrust and keeps an eye on the ramper ahead of the cockpit who is now giving the both-hands-twirling "continue powering back" signal. The two wingwalkers will give a signal to the cockpit ramper that it's time to stop. He will signal that to the cockpit and the captain takes off the reverse thrust and lets idle thrust bring the jet to a stop. A little forward thrust and by this time the FO is already getting the taxi clearance.
Last edited by Flying Trucker on Sun May 29, 2011 1:02 pm, edited 1 time in total.
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Re: Why?

Postby -Crossfire- » Sat May 28, 2011 3:18 pm

I've also seen lots of C-17 pictures where they are parked with the reversers open.
Last edited by -Crossfire- on Sat May 28, 2011 3:19 pm, edited 1 time in total.
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Re: Why?

Postby BigTruck » Sat May 28, 2011 11:22 pm

[quote]I've also seen lots of C-17 pictures where they are parked with the reversers open.
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Re: Why?

Postby Flying Trucker » Sun May 29, 2011 10:12 am

Good morning all... :)

This should have gone along with my original post but forgot to put it in... :)

http://www.airliners.net/aviation-forum ... ain/13745/

If you study the picture carefully, you can see that the cascaders are blocked underneath but open above...the exhaust is thrust forward and upwards.

With this system, you can keep the engines running and engage the idle reverser system and just immediately begin to load or unload without having to shut down and restart the engine. The C-17 was designed for missions where you land at an airfield, immediately unload and/or load troops and cargo and takeoff immediately. Jet engines take a while to start up and get them up to speed. Its basically a time saving measure and it also prevents your troopers and cargo from being blown all over the ramp.

Thats why you saw the reversers engaged when the C-17 was parked, its only to prevent jetblast from blowing everything around and you can offload off the aircraft as soon as it stops, instead of having to wait for the engine to spool down before its safe to access the plane.

Airliners on the other hand, they aren't designed to land on unpaved runways, only paved runways and they're usually free of debris, so this kind of reverser system is not quite necessary. Jet engines can only take a certain amount of punishment from FOD before they conk out, but what are the chances of having a really dirty runway at a major airport?
Last edited by Flying Trucker on Sun May 29, 2011 10:15 am, edited 1 time in total.
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Re: Why?

Postby BigTruck » Wed Jun 01, 2011 8:06 pm

Great info Doug!  :)
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Re: Why?

Postby -Crossfire- » Thu Jun 02, 2011 9:59 am

Thanks Doug,

I never though about the engines running while they load/offload, but it makes perfect sense.

I can do the same thing in the King Air by feathering the props on the ground!
Last edited by -Crossfire- on Thu Jun 02, 2011 10:00 am, edited 1 time in total.
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Re: Why?

Postby Flying Trucker » Thu Jun 02, 2011 1:10 pm

You are all welcome... ;)
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