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Posted: 3/19/2006 11:49:25 AM EDT
[Last Edit: 3/19/2006 11:51:18 AM EDT by AyeGuy]
What is the purpose of the cut-away center section of the engine nacelle? It is open to the outside and has a white grid covering:



This C-16 was minty new with 400 flight hours:



A HUD on a cargo plane? What will they think of next!



Here I am at the controls, preparing to take off. Always look like confident in front of the troops, even if you don't know what the bleep you are doing!

Link Posted: 3/19/2006 11:50:53 AM EDT
not sure about the white grate on the engine nacelles, but the HUD is a handy adaptation for low level night drops like the C-17 is designed to do.

IIRC, they are putting them in the new J model C-130 as well
Link Posted: 3/19/2006 11:53:07 AM EDT
talk to brohawk he is a c-17 guy
Link Posted: 3/19/2006 11:55:00 AM EDT
[Last Edit: 3/19/2006 11:58:13 AM EDT by KA3B]
Engine thrust reverser.
Link Posted: 3/19/2006 11:56:04 AM EDT
The thrust reversers are just open.
Link Posted: 3/19/2006 12:01:38 PM EDT
The white grates are where the fan exhaust is ducted.

The grates on the core (ass end) is where the cort exhaust is ducted.




The four engines are Pratt & Whitney PW2040 series turbofans, designated by the Air Force as the F117-PW-100.

Each engine produces 40,440 pounds of thrust, located on pylons ahead of and below the wing leading edge.

The engines are equipped with directed-flow thrust reversers capable of deployment in flight.

On the ground, a fully loaded aircraft, using engine reversers, can back up a 2 percent slope.

Two of the nacelle design features account for the C-17's capability to make extreme short-field landings at heavy gross weights: propulsive lift technology and an advanced thrust reverser design.

Propulsive lift results from directing engine exhaust across both sides of the flap.

Combined with the advanced thrust reversers, propulsive lift enables short landings. The thrust reversers are an integral part of the C-17 nacelle.

When thrust reversal is initiated, both fan and core exhausts are redirected.

Thrust is directed forward and upward through exposed louvers for maximum reverse thrust.

During ground operations, the thrust reversers can be deployed with engines idling, directing engine blast away from personnel working cargo.



Link Posted: 3/19/2006 12:16:17 PM EDT
Link Posted: 3/19/2006 12:27:45 PM EDT

Originally Posted By vito113:
I've heard the C-17 can lose altitude at over 20,000ft/min on a tactical approach!!!!!



Drop the flaps and gear, push the throttles past the gate into reverse, lower the nose and trim the aircraft up and there ya go....

Link Posted: 3/19/2006 12:29:53 PM EDT
Flown on one to Rota in 1996...Awesome plane.
Link Posted: 3/19/2006 12:45:43 PM EDT
If they did that will we were jumping the crew chief would be cleaning up alot of puke

FREE



Originally Posted By vito113:
I've heard the C-17 can lose altitude at over 20,000ft/min on a tactical approach!!!!!

Link Posted: 3/19/2006 12:53:14 PM EDT

Originally Posted By KA3B:

Originally Posted By vito113:
I've heard the C-17 can lose altitude at over 20,000ft/min on a tactical approach!!!!!



Drop the flaps and gear, push the throttles past the gate into reverse, lower the nose and trim the aircraft up and there ya go....





Is that possible? In flight, no touch down swithes activated?

Just curious, or are the stops in the throttle quadrant all that's there?



Link Posted: 3/19/2006 12:57:12 PM EDT
[Last Edit: 3/19/2006 12:58:15 PM EDT by tangeant]
Shouldn't be able to move throttles into reverse unless you have gear down & weight on wheels.

He probably meant to say throttles to flight idle.
Link Posted: 3/19/2006 12:58:18 PM EDT

Originally Posted By Slick44Magnum:
The thrust reversers are just open.



Does that mean the whole rear half of the nacelle slides rearward to expose the grate, and that in regular thrust mode it slides forward so that the grate is covered and the nacelle is smooth and un-interrupted?
Link Posted: 3/19/2006 1:03:39 PM EDT

Originally Posted By AyeGuy:

Originally Posted By Slick44Magnum:
The thrust reversers are just open.



Does that mean the whole rear half of the nacelle slides rearward to expose the grate, and that in regular thrust mode it slides forward so that the grate is covered and the nacelle is smooth and un-interrupted?



Yes. When you fly next time get a seat near the engine, just in front of it. You can see the thrust reversers work when they land. The rear cowling will slide backwards and you can hear and feel the pilots give more rpms. The spoilers and brakes also slow the plane. Its quite dramatic how well they work.

Suposedly one of those suckers deployed in flight on a 767 causing it crash.
Link Posted: 3/19/2006 1:07:21 PM EDT

Originally Posted By FREEFALLE7:
If they did that will we were jumping the crew chief would be cleaning up alot of puke

FREE



Originally Posted By vito113:
I've heard the C-17 can lose altitude at over 20,000ft/min on a tactical approach!!!!!




In my book that's something the load had to fix.
Link Posted: 3/19/2006 1:07:52 PM EDT
Heres a C-130 on a combat approach.Hold on to yer lunch!

http://www.alexisparkinn.com/photogallery/Videos/2006_c130_amazing_approach.wmv
Link Posted: 3/19/2006 1:11:57 PM EDT
[Last Edit: 3/19/2006 1:13:03 PM EDT by vito113]
Link Posted: 3/19/2006 1:16:07 PM EDT
Link Posted: 3/19/2006 1:21:21 PM EDT
Originally Posted By FREEFALLE7:
If they did that will we were jumping the crew chief jumpmaster would be cleaning up alot of puke

FREE


Fixed it for ya!

Crew Chief's don't clean up puke when there is at least one jumpmaster aboard.

We were dropping troops at Pope/Ft. Bragg (back in 93/94) in C-130Es, some of the troops started puking in between the seats and on the floor. When we landed the female jumpmater aboard gathered her gear and started to deplane; my DCC explained that since the puke didn't leave with her jumpers, she was going to clean it up. She really didn't seem that upset, just cleaned it up and moved on.

Can't say I ever wanted to jump out of an airplane; God bless those crazy bastards that do!

B_S
Link Posted: 3/19/2006 1:53:39 PM EDT
[Last Edit: 3/19/2006 1:57:15 PM EDT by Chairborne]

Originally Posted By tangeant:
Shouldn't be able to move throttles into reverse unless you have gear down & weight on wheels.

He probably meant to say throttles to flight idle.



Actually Vito is right, they will go into reverse in flight. They decend at about 300 knots btw, from what the -1 says, and what the crews tell me. It's pretty messy in the cabin when they do hard TAC-Ds and all the chains come out of their lockers, all the rails pop up, and all the dirt in the floor is ON the floor. The crew was gracious enough to clean up their mess though, we just had to grab the shop vac for them. The engines were designed to reverse in flight specifically for TAC-Ds, in fact, two of the engines on a C-5 will do it too (I think its the inboards, but not sure). The core thrust reversers don't actually "reverse" much at all, but they make engine running cargo loading/offloading safer, less chance of getting cooked behind the motors. Some of our guys that were hauling jearheads for the tsunami relief said they goaded them into "doing something cool" so they did a really gnarly TAC-D and had about half the guys puking.

ETA: The worst thing about T/Rs is standing in front of them in the desert, when its 130* ambient and they heat it up even more, waiting to marshall them out (backwards, of course). It'll make an unbearable day even worse. It is cool to be able to back them up as far as we need to though, gives us some very "interesting" parking options, like putting 12 of them where 4 were supposed to go.
Link Posted: 3/19/2006 1:56:01 PM EDT

Originally Posted By vito113:

Originally Posted By realwar:
Heres a C-130 on a combat approach.Hold on to yer lunch!




Made hot…

www.alexisparkinn.com/photogallery/Videos/2006_c130_amazing_approach.wmv



HOLY HELL
Link Posted: 3/19/2006 3:16:35 PM EDT
IIRC there is no spent exhaust gas on some reversers, just the air coming off the compressor section.
Link Posted: 3/19/2006 3:41:23 PM EDT

Originally Posted By ZitiForBreakfast:
IIRC there is no spent exhaust gas on some reversers, just the air coming off the compressor section.



Actually, it's air from the fan. The large fan you see looking into the front of the engine. In a modern high bypass turbofan engine, the majority of the engines thrust is produced by this fan.

Cascade thrust reversers simply re-direct the path of the fan air. The clamshell reversers close over the exhaust, and redirect the exhaust gasses, as well as the fan air.
Link Posted: 3/19/2006 3:44:26 PM EDT
I don't get it. Wouldn't the thrust just come out radially from the engine through the grate, not vectored towards the rear?
Link Posted: 3/19/2006 3:56:08 PM EDT

Originally Posted By AyeGuy:
I don't get it. Wouldn't the thrust just come out radially from the engine through the grate, not vectored towards the rear?



The reversers are deployed, the air is redirected through the grates, vectored toward the front of the aircraft. So its slowing it down. The rear exhaust is closed off.

You need to see DC9. The reversers are two halves of the rear cowling. The split like a clam shell and make a v toward the rear. The exhaust hits the inside of the V and is redirected forward. A fan has the same concept except the mechanism is inside.
Link Posted: 3/19/2006 3:59:51 PM EDT

Originally Posted By AyeGuy:
I don't get it. Wouldn't the thrust just come out radially from the engine through the grate, not vectored towards the rear?



The big deal is that since the air is no longer going out the back of the engine, it is no longer pushing you along. The smaller benefit, is that since the air is ducted forward, it now slows the airplane down.

The airplane I now fly, has the clamshell type of reversers, and simply opening them provides you with lots of deceleration.

The last airplane I flew, had the cascade type of reversers. We had to select maximum reverse thrust to feel much deceleration.

None of the civil transport airplanes I've ever flown could use the reverse in the air, so I've never experienced that. But it must be quite a ride.

When we train in the Simulator, for a reverser deployment in flight, the whole thing shakes like crazy. I cant imagine opening two of them, and taking the express elevator down.
Link Posted: 3/19/2006 4:28:23 PM EDT
Years ago, a Russian transport aircraft crashed, killing all on board.

The investigation found that the pilot had allowed his young son into the cockpit and had allowed him to sit in the captain's position. The kid accidentally turned on the thrust reversers, IIRC, and the crew could not regain control in time to save the aircraft.
Link Posted: 3/19/2006 4:28:28 PM EDT

Originally Posted By Chairborne:

Originally Posted By tangeant:
Shouldn't be able to move throttles into reverse unless you have gear down & weight on wheels.

He probably meant to say throttles to flight idle.



Actually Vito is right, they will go into reverse in flight. They decend at about 300 knots btw, from what the -1 says, and what the crews tell me. It's pretty messy in the cabin when they do hard TAC-Ds and all the chains come out of their lockers, all the rails pop up, and all the dirt in the floor is ON the floor. The crew was gracious enough to clean up their mess though, we just had to grab the shop vac for them. The engines were designed to reverse in flight specifically for TAC-Ds, in fact, two of the engines on a C-5 will do it too (I think its the inboards, but not sure). The core thrust reversers don't actually "reverse" much at all, but they make engine running cargo loading/offloading safer, less chance of getting cooked behind the motors. Some of our guys that were hauling jearheads for the tsunami relief said they goaded them into "doing something cool" so they did a really gnarly TAC-D and had about half the guys puking.

ETA: The worst thing about T/Rs is standing in front of them in the desert, when its 130* ambient and they heat it up even more, waiting to marshall them out (backwards, of course). It'll make an unbearable day even worse. It is cool to be able to back them up as far as we need to though, gives us some very "interesting" parking options, like putting 12 of them where 4 were supposed to go.



The C-5 doesn't use the TRs for TAC-Ds. The standard saying when using them was not to use them unless you're ready to stay there for at least 5 days. The rumor is that the C-5 crash at Ramstein during GW1 was caused by a TR extending at takeoff thrust causing the aircraft to flip over and crash. Most of the old-heads would never use the TRs unless they could be inspected on the ground prior to taking off.

Spooky
Link Posted: 3/19/2006 4:30:01 PM EDT
The grates look very clean; so the thrust that comes out here is just uncombusted air?
Link Posted: 3/19/2006 4:35:36 PM EDT

Originally Posted By AyeGuy:
The grates look very clean; so the thrust that comes out here is just uncombusted air?



That's correct. The air from the bypass fan never takes part in any combustion. Depending on the engine, less than 1/2 of the air that goes in the front ever sees fuel or fire.

The rest of the air bypasses the compressor section. That's where the term hi-bypass comes from.
Link Posted: 3/19/2006 4:42:17 PM EDT

Originally Posted By ZitiForBreakfast:
Is that possible? In flight, no touch down swithes activated?
Just curious, or are the stops in the throttle quadrant all that's there?



Do you guys bother to READ my posts?
Link Posted: 3/19/2006 4:43:58 PM EDT

Originally Posted By vito113:
I've heard the C-17 can lose altitude at over 20,000ft/min on a tactical approach!!!!!


<ding> This is your Captain speaking. We are going to begin our approach so please secure your belongings and I am going to turn on the seat belt light. Thank you for flying Southwest.
Link Posted: 3/19/2006 4:50:38 PM EDT
[Last Edit: 3/19/2006 4:53:08 PM EDT by AyeGuy]
Forgive me for being dense, but does the air go backwards through the fan, in through the grate, out through the front inlet cowling? Surely the fan does not go into reverse...or do the fan blades have variable pitch, like a propeller?



Hi KA3B! Someone help this guy too!
Link Posted: 3/19/2006 4:56:09 PM EDT
The CFM-56-2A that the Navy's E-6B uses has translating engine cowls that are part of the thrust reverse system.

They can not be deployed in flight.

Link Posted: 3/19/2006 4:59:51 PM EDT

Originally Posted By AyeGuy:
Forgive me for being dense, but does the air go backwards through the fan, in through the grate, out through the front inlet cowling? Surely the fan does not go into reverse...or do the fan blades have variable pitch, like a propeller?



Hi KA3B! Someone help this guy too!




The bypass air that the fan produces (hehe, follow along with that) is blocked by a set of "doors" or a "translating cowl" that blocks the bypass air from going out the ass-end and reverses the bypass air to go out the OPEN GRATE of the cowling. The air path has been reversed.

Any questions?

Jet engine 101 was held last year.

Link Posted: 3/19/2006 5:00:21 PM EDT
Originally Posted By AyeGuy:
Forgive me for being dense, but does the air go backwards through the fan, in through the grate, out through the front inlet cowling? Surely the fan does not go into reverse...or do the fan blades have variable pitch, like a propeller?



No, the reverser grates are aft of the fan. So the air still goes thru the fan. When you select reverse, the cowls open (exposing the grates) and the inside of the nacelle (between the engine, and the nacelle) are blocked off. The only way out for the air then is thru the grates.

Think about it like this. The actual "power" part of the engine is much smaller than the nacelle, let's just say half as big. The fan air normally just flows around the "engine", and out the back. Where it mixes with the hot exhaust air. The reversers just re-direct that "outside air". The engine and fan never change directions.

IIRC, certain versions of the DC-8, and the concorde could use reverse in flight as well.
Link Posted: 3/19/2006 5:05:27 PM EDT
Link Posted: 3/19/2006 5:08:01 PM EDT
It's kind of hard to see, but gives you the general idea.

Link Posted: 3/19/2006 5:09:06 PM EDT
It's all explained right here....

Link Posted: 3/19/2006 5:19:43 PM EDT

Originally Posted By vito113:
I've heard the C-17 can lose altitude at over 20,000ft/min on a tactical approach!!!!!



This is true. I've been on C-17's during several tactical approaches.

Almost as much fun as going in reverse down the runway at a high rate of speed.
Link Posted: 3/19/2006 5:26:01 PM EDT
They can do that?
Link Posted: 3/19/2006 5:29:14 PM EDT
.
Link Posted: 3/19/2006 6:57:32 PM EDT
Is the number REALLY 20Kft/min? Hell, the space shuttle does 14Kft/min at 300KN. This thing can drop faster in a controlled fashion than the space shuttle?

Who's got a -1 page they can post on that?

aa
Link Posted: 3/19/2006 7:11:02 PM EDT
[Last Edit: 3/19/2006 7:11:18 PM EDT by JustinOK34]
They don't use max reverse in flight for the tactical descents, just flight idle.

Wicked shit.

Oh, the E-3 can get up to around 9,000 fpm descent with speed brakes up and gear down.
Link Posted: 3/19/2006 7:35:10 PM EDT
I watched one backing up a slope in front of a hanger in Saudi once. It was amazing to watch the vortex of sand being sucked into the engines and being spit out as black smoke. From what I hear the sand doesn't do too much damage either. I had to clean up the mess on the taxiway and runway at Ft Lewis when that female pilot destroyed the engines on the C-17 by reving it up with engines hanging out off of the paved surface.
Link Posted: 3/19/2006 7:51:05 PM EDT
Looks like somebody else was at Mather today too.
Link Posted: 3/19/2006 7:56:48 PM EDT

Originally Posted By JustinOK34:
They don't use max reverse in flight for the tactical descents, just flight reverse idle.

Wicked shit.

Oh, the E-3 can get up to around 9,000 fpm descent with speed brakes up and gear down.



Fixed it for ya, they do open the reversers.
Link Posted: 3/19/2006 8:00:11 PM EDT

Originally Posted By Wirebrush:
I watched one backing up a slope in front of a hanger in Saudi once. It was amazing to watch the vortex of sand being sucked into the engines and being spit out as black smoke. From what I hear the sand doesn't do too much damage either. I had to clean up the mess on the taxiway and runway at Ft Lewis when that female pilot destroyed the engines on the C-17 by reving it up with engines hanging out off of the paved surface.



Yeah that one down at Gray Field really did a number on those motors. Many damaged fan blades and stators. The sand definitely doesn't do much to these motors, the fan blades pretty much sling it to the outside so it doesn't get in the compressor, and the fan blades are pretty tough. I have seen some pretty dang big dings and dents that nobody knew where there till they inspected it, birds and big rocks I guess. For the naysayers, I will get a copy of the -1 for tactical decents, and translate only the relevant parts here. (tomorrow, I just got home from work)
Link Posted: 3/19/2006 8:57:10 PM EDT
I found this Tactical Descent procedure using only open source means (google, of course), so don't yell about opsec please.

17.12. Tactical Descents. If necessary, reverse engine idle thrust and speed brakes can be used to obtain rapid descents from high altitudes. Initial descent rates of over 12,000 fpm may be achieved. Tactical descents are always flown single ship and use of the flight director for guidance is recommended.
17.12.1. High-Speed Rapid Descent. Use the following procedures:
17.12.1.1. Select "320 PCH" (or .800 Mach when above 28,000 feet) on the AFCS panel. Disconnect the autopilot, extend the speedbrakes, and deploy reverse idle thrust (if desired). ("Speedbrakes" means all spoilers fully deployed and partial flaps, all automatically programmed through the flight control system)
17.12.1.2. The PF follows the pitch bar to maintain desired speed, and follows the roll bar for lateral navigation guidance.
17.12.1.3. At the briefed "start level off" point, the PNF will make an advisory call to the PF. The
level off should be initiated approximately 2,000 feet above the desired altitude.
17.12.1.4. Stow thrust reversers (if used) and speed brakes prior to leveling off. Select desired
speed (IAS on THR) on the AFCS panel and establish en route airspeed.
Link Posted: 3/19/2006 9:01:47 PM EDT

Originally Posted By PinePig:
Looks like somebody else was at Mather today too.



The simulated A-10 attack was bitchin'

And the Heritage flight when it flew in formation with the P-51 was amazing as well.

I grew up on that base
Link Posted: 3/19/2006 9:06:48 PM EDT
Ha, that was cool. You guys think that is scary? Shit, Id like to do that in the Cessna I fly.
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