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litz
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RE: DL MD-80 Off Runway At LGA - Part 2

Wed Mar 11, 2015 6:47 pm

Quoting maxpower1954 (Reply 146):
Aircraft type is important - a "good" report from a A321 means much more than "good" from an A319 because of the large weight differential. It can vary dramatically over the entire length of the runway.

Per the latest NTSB update, one of the previous aircraft (3 minutes prior) that reported "good" was, in fact, another DAL MD-88 ...

Maybe it had newer tires? Don't know ...

NTSB report did say it impounded the FDR from that flight as well, so they'll have data from its landing to play with as well ...
 
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NWAROOSTER
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RE: DL MD-80 Off Runway At LGA - Part 2

Wed Mar 11, 2015 7:29 pm

Quoting wjcandee (Reply 145):

I'm not understanding why the papers are all referring to the brakes as the reason for the loss of directional control. Maybe in the big picture (no brakes means slower reduction in speed means more lift means less adhesion, and means pilot might use higher EPR on reverse thrust means less rudder authority to provide directional stability. But it's pretty-circuitous. I read the headlines and thought they were talking about asymmetric braking, but if there were NO autobrakes (and no manual brakes applied?), then the link between brake and runway departure isn't a direct one.

Does the MD-80 series aircraft even have nose wheel brakes? There tires are awful small. I know Northwest Airlines took the nose wheel brakes off their 727s. They were not effective, a maintenance headache and added weight to the aircraft. I never worked the DC-9, so I do not know if they had nose wheel brakes.   
Procrastination Is The Theft Of Time.......
 
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DL_Mech
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RE: DL MD-80 Off Runway At LGA - Part 2

Wed Mar 11, 2015 7:42 pm

Quoting NWAROOSTER (Reply 151):
Does the MD-80 series aircraft even have nose wheel brakes?

None of the Douglas twinjets have nose wheel brakes.

Quoting NWAROOSTER (Reply 151):
I know Northwest Airlines took the nose wheel brakes off their 727s. They were not effective, a maintenance headache and added weight to the aircraft.

I've only seen one 727 with the nose brakes, an ex Pan Am shuttle -243.
This plane is built to withstand anything... except a bad pilot.

Former AMT on A220,A310,A319/20/21,A330,A350,B707,B717,B727,B737,B747,B757,B767,B777,DC-9,DC-10,L-1011,
MD-80/90,MD-11
 
AIRWALK
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RE: DL MD-80 Off Runway At LGA - Part 2

Wed Mar 11, 2015 8:00 pm

Quoting DashTrash (Reply 149):
Not in anything I've flown. Must have weight on wheels to open the buckets.

It was actually possible to engage them mid-flight in other types, a Lauda flight (767) had an accidental deployment which was believed to have led to the accident. Boeing modified it thereafter, by adding sync-locks, which prevent the thrust reversers from deploying when the main landing gear truck tilt angle is not at the ground position.
I'm sure this thread will take off soon
 
cbphoto
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RE: DL MD-80 Off Runway At LGA - Part 2

Wed Mar 11, 2015 11:31 pm

Quoting DTWPurserBoy (Reply 140):
Hey pilot friends....is this true?
Quoting DashTrash (Reply 149):
Uh..... Not in anything I've flown. Must have weight on wheels to open the buckets. I know the DC-8, as you're discussing could use the inboard reversers in flight, the C-17, and some Soviet designs as well, but that's it to my knowledge.

Quote from a technical book I have on the 80 reversers.

"Each thrust reverser has two, hydraulically operated, doors.The reverser lever on the throttle controls the position of the doors, as well as the reverse power setting. The lever can only be moved into the reverse range when the throttle is in the idle position. Initial aft movement of the lever to its interlock stop releases the door safety latch, deenegizes the shutoff valve solenoid and moves the reverser control valve into reverse position.

When the doors are extended to reverse position, the interlock stop will be released, allowing maximum reverse thrust operation.

Observe - there is no technical device that will prevent the pilot from applying reverse thrust at FL 310. The system is "failsafe" but not "fool proof"

Something that we were taught numerous times throughout ground school on the MD-80.

Also, the emergency memory item for a bucket deployment in flight, is to bring the affected throttle immediately to idle, and verify the reverse lever is in the "full down" position, as their is nothing preventing it from engaging in flight. It is important for the general public to know, that a bucket deployment in flight on the MD-80 is NOT a catastrophic event, with the correct training and a quick response from the crew. It is something we train for in the simulator on a fairly regularly bases.

That being said, regardless of the ground spoiler position or auto brake function, the reverse thrust system can be engaged prior to the wheels having weight on them, which given different spool up times, could very well cause a significant yawing motion on the plane.
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northwestEWR
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 12:32 am

Quoting cbphoto (Reply 154):

Almost word for word what's in the DL M88/M90 Flight Operations Manuals. Nothing is mentioned on the 88 side about requiring weight on wheels but it is explicitly mentioned as a requirement on the MD-90. Not sure if that's just something that was left out and then added for the 90, or it's really possible.

Theoretically you could move the throttles to idle and then activate reverse thrust IF you aren't required to have WOW. So far I don't see anything that says this is a requirement on the 80s.

FWIW: The Delta manuals explicitly and repeatedly forbid the use of any reverse thrust (even idle) until the nose wheel is on the ground. They also caution against reverse about 1.3EPR (but certainly don't forbid it, just be aware)

They also permit flight operations with one thrust reverser inop so I don't think it's as big a deal as others are suggesting. This accident sounds like something else.

[Edited 2015-03-11 17:33:04]
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71Zulu
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 1:17 am

Quoting northwestEWR (Reply 155):

Almost word for word what's in the DL M88/M90 Flight Operations Manuals. Nothing is mentioned on the 88 side about requiring weight on wheels but it is explicitly mentioned as a requirement on the MD-90. Not sure if that's just something that was left out and then added for the 90, or it's really possible.

A DL M88 made an emergency landing at MSY a few years ago reporting a vibration. The pilot told ATC they suspected thrust reverser deployment in flight.
 
cbphoto
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 2:12 am

Quoting northwestEWR (Reply 155):

Yeah, it might have been a design change on the 90 to add the WOW. After all, the 90 doesn't have buckets, and has the more conventional reverse doors on the engine.

I would be curious to know the dispatch protocol, with a bucket MEL'd on a contaminated runway? I would guess breaking action would have to be Good, otherwise I could foresee some issues landing and deploying just one bucket on anything less, could get dicey.

While I'm not sure by any means the specifics of the LGA incident, deploying the buckets and reverse thrust, while hydroplaning on a thin layer of snow, could cause some controllability issues, especially the way the 80s spool up out of sync.
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northwestEWR
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 2:53 am

Quoting cbphoto (Reply 157):

That'd be MEL 78-00-01 -- Thrust Reverser Inop and it doesn't say anything about weather restrictions or runway conditions. So as far as dispatching it into snowy conditions, that's a green light. Especially on days where the majority of the 88 ops are going to see snow making an aircraft swap pointless.

The only real mention of thrust reversers and poor runway conditions is in the Flight Crew Training Manual and it says:

Quote:
Landing on Slippery or Wet Runways
During landing rollout on a slippery runway with a crosswind, directional control problems may develop. Apply reverse thrust cautiously when landing on slick surfaces.
• Allow engines to spool up at a low power setting, then apply reverse thrust slowly and symmetrically.
• For increased directional control, exert forward control wheel pressure in order to maintain positive nose wheel traction. Avoid excessive pressure.
• If a skid condition develops, return both reverse levers to the IDLE detent.
• If the airplane starts to weathervane into the wind: • Reduce reverse thrust to reverse idle.
• Disconnect the autopilot, if engaged.
• Release the brakes.
• Use rudder pedal steering and differential braking to correct back to runway track. It is not necessary to immediately correct to runway centerline as this may delay deceleration efforts and aggravate skid conditions.
• When re-established on runway track, apply maximum braking and symmetrical reverse thrust to stop the airplane.
• Consider leaving engines in idle reverse until ability to stop, or clear the runway, is assured.

CAUTION: Reverse thrust above 1.3 EPR may blank the rudder and degrade directional control effectiveness. However, as long as the aircraft is aligned with runway track, reverse thrust may be used as necessary (up to maximum), to stop the aircraft.

There's a conflict in the training manual--the caution note would apply but if you're going into LGA and you only have 6,000 feet left after touchdown and conditions are poor--the last bullet point is key. "Consider...idle reverse...until ability to STOP..." Yes--there are rudder concerns, but stopping, especially on a short and snowy runway is going to take precedent. As long as the nose wheel is on the ground, you *should* be fine. This is where pilot's make their money.
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DashTrash
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 1:08 pm

Quoting cbphoto (Reply 154):

I stand corrected then.

Quoting northwestEWR (Reply 155):
They also caution against reverse about 1.3EPR (but certainly don't forbid it, just be aware)

I thought 1.3 EPR was a limitation on contaminated runways, 1.6 being target on clean runways? I'm not an 88 (or Delta pilot), just going off what a friend said.
 
hivue
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 2:52 pm

Quoting northwestEWR (Reply 155):
This accident sounds like something else.

The ground spoilers not deploying, right? I'm still interested in knowing if it's been established that the crew armed the spoilers.
"You're sitting. In a chair. In the SKY!!" ~ Louis C.K.
 
cbphoto
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RE: DL MD-80 Off Runway At LGA - Part 2

Thu Mar 12, 2015 6:21 pm

Quoting DashTrash (Reply 159):

You are correct! 1.3 EPR is the contaminated runway limitation, 1.6 EPR is the dry runway limitation.
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