cricri
Posts: 540
Joined: Sat Oct 02, 1999 12:10 am

Thrust Reverser Question

Sat Sep 30, 2000 7:58 pm

1 - Is it possible to use thrust reverser for landing on the remaining engine(s) while one or more are shut down due to a failure?
2 - How do u active the thrust reverser on most of the plane? i saw i.e. a 747 where u have to "delog" two swtiches to pull back. I mean, u just simply pull back to active them or are they switches?
 
Buff
Posts: 1066
Joined: Fri Mar 16, 2007 1:29 pm

RE: Thrust Reverser Question

Sat Sep 30, 2000 8:45 pm

1/ Yes, but with caution;

2/ Every airplane is different. Turboprops have various "gates" through which the power levers must be retarded - for instance, on the Twin Otter, one twists the handles on the power levers; on the Dash 7, a weight-on-wheels sensor automatically "opens" the stops to allow aft travel of the power levers; the Dash 8 requires lifting of toggle levers underneath the power lever grips; the BAe41 has a similar but more flimsy trigger to accomplish same. Boeing jets have a second set of smaller "thrust levers" on top of the regular thrust levers which a) activate the reverser sleeves, and b) accelerate the engine in reverse thrust mode. Airbus products are different again.

Best Regards,

Buff
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Thrust Reverser Question

Sun Oct 01, 2000 11:42 am

Every Boeing, MD and Fokker airliner I've flown has a second set of trottle handles forward of the primary handles. These are called Reverse Thrust Levers or Thrust Reverser Levers depending upon manufacturer. Upon landing pull Thrust Levers to idle, then reach forward and pull Reverser Levers up and aft. All have had a detent for idle reverse thrust position. Pulling farther aft increases reverse thrust. Pretty simple from an operator's viewpoint.  

Both turboprops I flew in the navy (E2 and T44) utilized the "power levers" for reverse thrust. On the T44 (a Beech Kingair with PT6 engines) you pulled the power levers aft to idle detent, paused for props to stabilize RPM, then pulled farther aft for reverse thrust blade angles. On the E2 (T56 engines) you pulled power levers aft to idle, lift upward 1-1/2 inches to get into beta range, then moved aft to get reverse thrust. Props always seem more complex. Especially for this simple mind.  
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
Buzz
Posts: 694
Joined: Sun Nov 21, 1999 11:44 pm

RE: Thrust Reverser Question

Sun Oct 01, 2000 7:56 pm

Hi Cricri, Buzz here. Buff did a pretty good job of explaing it. AAR90 also had some good points.
On the A320's that we've bought, there are a couple of small "paddles" that are forward of the thrust knobs. If the airplane is in idle thrust, curl your fingertips around the paddles, lift up, and both thrust knobs slide aft to give reverse thurst.
The paddles are mechanical interlocks, and just like in the Boeing and Douglas airplanes you have to be at idle power to deploy a thrust reverser. Most airplanes need to have a signal that says the landing gear is really on the ground also. Of course, there are exceptions: the DC-8 comes to mind
Can i lock out just one reverser? Yes, Us mechanics sometimes mechanically disable a reverser and let the airplane fly. Of course we have to jump through 3 or 4 hoops to get permission (Flight Dispatch, Routing, Acft Maint and Control). Sometimes the weather / runway is good where it's going and rather than ground the airplane for maintenence here at PDX, we'll let it continue someplace that has parts. But with only one thrust reverser, the pilots need to be on their toes when they roll out on landing.
g'day
Buzz Fuselsausage, Line Mechanic by night, DC-3 Crew Chief by choice.
 
cricri
Posts: 540
Joined: Sat Oct 02, 1999 12:10 am

RE: Thrust Reverser Question

Mon Oct 02, 2000 8:45 pm

Tx all, it comes now clearly to my confused mind...  
 
Guest

RE: Thrust Reverser Question

Mon Oct 02, 2000 11:24 pm

On the DC-9 the thrust reverse levers are as AAR90 described.

The JT8D9s are tail mounted on the fuselage. With a shut down engine, activating reverse thrust will cause the aircraft to yaw-- but, from what I've been told, not as pronounced as on a 737 with an engine slung under the wing.

Nevertheless, and I've mentioned this before, by pulling the thrust levers, BOTH REVERSE BUCKETS will, hopefully, still activate (barring any structural damage to the engine that has been shut down--based on the circumstances). By activating the bucket on the shut down engine, you are introducing drag to off-set the assymetrical reverse thrust condition.

Thrust reversers were designed to give the brakes a break. If the situation is not a dire emergency (precautionary shutdown, no emerg evac), and the runway long enough, I would avoid cycling the engines into reverse at all.

AAR-90. You were an E-2 bubba? When did you get out? I know an E2 Scope Doper callsign of "Millie" (USNA 1983??)
 
Guest

RE: Thrust Reverser Question

Fri Oct 06, 2000 1:02 am

I am afraid I have to disagree with DC-9CAPT. Assuming that you shut down the engine in flight and did not take off with one engine, by pulling the "T-Handle" you shut off all hydrastic power to that engine and the T/R will not deploy.
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Thrust Reverser Question

Fri Oct 06, 2000 10:55 am

>AAR-90. You were an E-2 bubba? When did you get out?

VAW-117 1982-85
VAW-110 1985-86
VAW-0285 1986-1991

>...by pulling the "T-Handle" you shut off all hydrastic power
>to that engine and the T/R will not deploy.

Depends upon engine design. All those I've flown shut off hydraulic fluid inbound to the engine, but never outbound. Additionally, every hydraulic thrust reverser I've operated had an accumulator backup operating mode so loss of hydraulic pressure would not effect thrust reverser deployment -- at least one deployment.  
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
fr8tdog
Posts: 120
Joined: Wed Feb 16, 2000 4:25 pm

RE: Thrust Reverser Question

Fri Oct 06, 2000 2:36 pm

On the SF34-
for Question 1
A) on the "A" model saab yes you have reverse but not deep reverse capability. the B model has deep reverse capability.... however in both models expect a severe yawing moment when in reverse. (11' props swingin out there.)
? # 2.  


On the SF34 there is an Idle stop that is an electric solinoid, works off of the WOW switches (weight on wheels). It prevents the pilots from putting the aircraft into beta or reverse whilst inflight. (American Eagle gave all of us that Mod) once the solinoid pin retracts then the PL can be pulled into ground idle (about 8 deg of pitch on the props) if reverse is desired then there are two triggers that are pulled up on the PL quadrant and PL's are then pulled aft for reverse.
 
Guest

RE: Thrust Reverser Question

Mon Oct 16, 2000 12:18 pm

I have seen light and medium twin jet aircraft reverse thrust to power back from a gate. Does the B757/B767 also back away from a gate under their own power or is reverse thrust taxiing prohibited on these heavy aircraft?

Thanx
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Thrust Reverser Question

Mon Oct 16, 2000 9:04 pm

>Does the B757/B767 also back away from a gate...

Both have the capability, but the B767 has never had the authority with any airline that I know of. Early in its life with AA, the B757 performed powerbacks at DFW only. That authority was removed about 6 months later as we were FODing an average of 2 engines a month.
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Thrust Reverser Question

Tue Oct 17, 2000 5:05 am

Just to add to Buff's & Buzz's posts only the A320 has the 'paddles' the remainder of the Airbus range have the conventional arrangement.

Some of the other post's here have intrigued me.

DC-9CAPT,

Activating the T/Rev on the shut down engine ? All the aircraft I have worked on (BAC 1-11, VC10, DC10, 707, 747, 757, Airbus A300, A310, A320 & A340) dead engine = dead T/rev.
Additionally I wouldn't have thought deploying the T/rev on a dead engine would off set yaw by an appreciable amount, if that was the case why doesn't the 747 have such a system ? Please explain more.

AAR90

Of all the hydraulic T/rev's I have worked on, not one has had an accumulator. What a/c has ?

Finally with the advent of carbon brakes the use of T/rev is not prefered, unless circumstances require it. Carbon Brakes are more efficient at high temp and wear less at those temps so the non use of T/rev saves wear & tear on the engines & extends brake unit life.
 
FDXmech
Posts: 3219
Joined: Sun Mar 19, 2000 9:48 pm

A/C With T/R Accumulaters

Tue Oct 17, 2000 5:24 am

The DC9/MD80 have an hydaulic accumulator on each thust reverser.
You're only as good as your last departure.
 
AAR90
Posts: 3140
Joined: Fri Jan 21, 2000 11:51 am

RE: Thrust Reverser Question

Tue Oct 17, 2000 11:18 am

>Of all the hydraulic T/rev's I have worked on, not one has had an accumulator. What a/c has?

MD90, MD80 and F100.

>Finally with the advent of carbon brakes the use of T/rev is not prefered, unless circumstances
>require it. Carbon Brakes are more efficient at high temp and wear less at those temps
>so the non use of T/rev saves wear & tear on the engines & extends brake unit life.

Haven't seen this in any operating manual to date. Perhaps the economics haven't shown themselves yet. The MD90 has rather large carbon brakes and while they may be efficient, they make for a terrible rollout from a passenger's perspective. So strong they'll lock up the wheel when rolling over painted stripes on the runway. If expecting to use any brakes, I now have to plan where on the runway I want to be to prevent anti-skid activation and subsequent very bumpy ride for the pax.   If able, I much prefer no brakes with idle or near idle reverse thrust.  
*NO CARRIER* -- A Naval Aviator's worst nightmare!
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Thrust Reverser Question

Wed Oct 18, 2000 12:00 am

AAR90

Thanks for the info.

It is Co. policy with the operator I work for that T.Rev not used unless conditions require it. This applies to A340 & 747-400. If T. Rev is used a Pirep is required.
 
Guest

RE: Thrust Reverser Question

Wed Oct 18, 2000 2:00 am

VC-10,

I will try to answer your questions. I have only one precautionary engine shut down in the DC-9 that is several years old, and never had to cycle into reverse onto the landing roll since we were light.

I didn't say you would use the deployed reverser to offset "yaw", you would apply opposite rudder for that and nosewheel steering when it became available. But the bucket, since it "theoretically" will deploy, would have a drogue chute effect, if you will, to offset the assymetrical thrust condition. In other words, that may help the rudder deflection, all that much more, in keeping the aircraft close to the centerline. Will it be appreciable? I haven't been in a situation to make that call--and hopefully won't be soon.

But, this discussion comes up due to an incident we had in Denver (Stapleton) in 1994 before I was hired. A fully loaded -9 lost an engine at V-1. Crew and pax just heard a load bang. The force, they later found out, blew the reverser bucket off. The crew declared and emergency and landed three minutes later. The conditions were marginal and the runway was icy. Unfortunately, the plane came in a litle high and hot, and they had to go into reverse. The cycle into reverse caused the plane to swerve off the runway--just missing a drainage ditch. The crew recovered and stopped the aircraft at the very end of the runway. The crew was unaware of the full damage extent and did everything right, but did not know the reverser had blown off. The after-action on this incident stated that the offset drag, had the reverser been there, may have made the swerve less drastic. So, appreciable may be a bad term, but then again, in an emergency, I'll take every card I can play.

As for the 747s, the RRs deploy the reverse in a sleeve, not a bucket. Therefore you don't have the drogue chute effect.

I would be interested in hearing about the BAC-111 (Tays???) and its accumulator. It would seem that the ability to deploy the buckets was good engineering on the part of Pratt and McDonnell. You asked for my input, I would be interested on your thoughts. Thanks.
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Thrust Reverser Question

Wed Oct 18, 2000 2:57 am

DC-9CAPT.

Thanks, I was forgetting that a DC-9 reverser buckets open into the surrounding airstream. The Spey (1-11) & Conway (VC10) and for that matter JT3D-7 T. Rev buckets or clamshells deploy within the jet pipe and the gasses exhaust through cascade vanes.

The 1-11 didn't have an accumulator, all the RR engine T Revs I worked on (less 757) were pneumatic in operation.
 
crjmech
Posts: 257
Joined: Wed Jun 07, 2000 6:31 am

Deferred T/R And Fadec Question

Thu Oct 19, 2000 5:00 am

A co-worker of mine recently returned from a tour in DCA and related a story to me. An aircraft (EMB-145) came in with one T/R deferred and the captain complaining that he was unable to pull max reverse thrust on the engine with the good T/R. Since my friend was a CRJ guy and unfamiliar with the nuances of the ERJ, he called the EMBRAER help desk. They told him that this is a perfectly normal situation- the FADEC on the good engine will limit the reverse thrust produced in order to offset assymetrical thrust on rollout. Is this SOP for other FADEC equipped aircraft?
Thou shalt mind thine altitude,lest the ground reach up and smite thee.
 
VC-10
Posts: 3546
Joined: Tue Oct 26, 1999 11:34 am

RE: Thrust Reverser Question

Thu Oct 19, 2000 6:27 am

To prevent assymetric reverse thrust on the A340, both otbd engines are limited to idle power until both otbd reversers are fully deployed.

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