CO1404 off runway at DIA

[kevin47881]

Thanks for asking - the last word we have is they (Continental) was talking with the Ecuadorian consulate to assist in replacing her passport without requiring her to travel to Los Angeles or Chicago for a face to face meeting - the normal requirement. They also are working with someone (State department?) to replace her green card, I'm told.

We heard that carry on (and maybe checked?) bags have been recovered from the aircraft, are being assessed, inspected, cleaned (?) and hopefully they can begin to return salvageable belongings to the passengers soon - perhaps as soon as next week.

That's very good news, Greg.

 

[wabower]

It's an oral question at Simuflite.

Manageable <> Negligible, at least to an engineer like me:smile:.

Do you jet jocks even mention Vmc in your training? If not, then my guess would be that the airplane is designed with enough rudder that the wings stall first, and like you say, it's a complete non-issue operationally.

 

[sba55]

I'd also guess that the automatic rudder pushers have something to do with the lack of Vmc discussion...

 

[Greg Bockelman]

I'd also guess that the automatic rudder pushers have something to do with the lack of Vmc discussion...

Do you mean the YAW Dampers? Or are you talking about the Thurst Augmentation Computer, or whatever TAC is called?

 

[sba55]

Do you mean the YAW Dampers? Or are you talking about the Thurst Augmentation Computer, or whatever TAC is called?

I'm not sure. Maybe it's just the yaw dampers, but I thought it was it's own distinct system. What's the system that automatically applies rudder when an engine fails? On an airplane without autothrottles.

 

[Diana]

Thanks for asking - the last word we have is they (Continental) was talking with the Ecuadorian consulate to assist in replacing her passport without requiring her to travel to Los Angeles or Chicago for a face to face meeting - the normal requirement. They also are working with someone (State department?) to replace her green card, I'm told.

We heard that carry on (and maybe checked?) bags have been recovered from the aircraft, are being assessed, inspected, cleaned (?) and hopefully they can begin to return salvageable belongings to the passengers soon - perhaps as soon as next week.

Greg, thanks for the update. Hopefully she won't have to travel far to get her passport replaced.

 

[Teller1900]

I'm not sure. Maybe it's just the yaw dampers, but I thought it was it's own distinct system. What's the system that automatically applies rudder when an engine fails? On an airplane without autothrottles.

Ahhh, Rudder Boost. At least that's what they called it on the 1900. I don't know how wide spread that is, though. The 1900 is a real handful in a V1 cut if the autofeather doesn't, so I think that might have been a Beech thing to help keep our pointy end forward. It was tied in to the yaw damp computer/actuators, but technically a separate system. The Q doesn't have anything of that sort (thought we do have a stick shaker/pusher to keep us away from a stall), and I haven't heard anyone who flies anything else talk about a rudder boost system . FWIW, Vmc was not mentioned or demonstrated during training for either plane.

 

[flyingcheesehead]

Ahhh, Rudder Boost. At least that's what they called it on the 1900. I don't know how wide spread that is, though. The 1900 is a real handful in a V1 cut if the autofeather doesn't, so I think that might have been a Beech thing to help keep our pointy end forward. It was tied in to the yaw damp computer/actuators, but technically a separate system. The Q doesn't have anything of that sort (thought we do have a stick shaker/pusher to keep us away from a stall), and I haven't heard anyone who flies anything else talk about a rudder boost system . FWIW, Vmc was not mentioned or demonstrated during training for either plane.

I've heard it's on King Airs too. Must be a Beech thing, and since Felix is a Beech thing too...

 

[Fast n' Furious]

Rudder boost, rudder bias, TAC...whatever you want to call it is a certification requirement. If the airplane in question requires more than 150 pounds of force on the rudder pedal for you to maintain directional control in an engine out situation, you're going to have some type of augmentation. Here's a really neat discussion of engine out aerodynamics where rudder augmentation is discussed. Find a comfy chair and a snack:

http://uk.geocities.com/alf5071h@btopenworld.com/Vmca.ppt#256,1,Aircraft Control at Airspeeds Near Air Minimum Control Speed VMCA

 

[RotorAndWing]

I've heard it's on King Airs too.

A King Air is a hand full on an engine out.

On the B727 we have an upper rudder, lower rudder. These are hydraulically powered and also include a "standby" hydraulic power to the lower rudder.

While the flaps are out of the "up' position you have full hydraulic pressure to the lower rudder and once the flaps are up that decreases to about half.

 

[AirVenture]

I've heard it's on King Airs too. Must be a Beech thing, and since Felix is a Beech thing too...

Nope, not on the Beechjet, bummer! However, that could be because of it's Mitisubishi forefathers. The most single-engine rudder pressure I've had to hold is on the darn Twin Comanche! That's partly because I have to have my seat pretty far back so my knees don't get tangled in the yoke.

 

[Everskyward]

I've heard it's on King Airs too. Must be a Beech thing, and since Felix is a Beech thing too...

Nah, it's more than a Beech thing. The Hawker had it (while it was still British, before it became a Beech) and so does the CE-680. The Lear 35 didn't have it but maybe the rudder forces didn't exceed 150 lbs without it.

Here is a simple (I hope) explanation of a rudder bias system.

 

[Greg Bockelman]

I'm not sure. Maybe it's just the yaw dampers, but I thought it was it's own distinct system. What's the system that automatically applies rudder when an engine fails? On an airplane without autothrottles.

Can't answer that, Felix. All I can speak to is the 777. The 737 didn't have such system and I don't remember about the A-320. Well let me recant a bit. Those airplanes had yaw dampers, which won't add rudder in a failure, but they didn't have TAC, whose sole purpose IS to compensate for an engine out scenario.

 

[TangoWhiskey]

Additional info from an airline pilot, to supplement the article quoted below.

If you use the steering "tiller" to turn the nose wheel, you are not moving the rudder. The steering tiller gives you more left and right motion of the nose wheel than the rudder pedals, but past a certain point, depending on speed, the nose wheel will start skidding sideways and will lose the ability to turn the aircraft.

It's possible he was applying full rudder and felt he needed the extra nose-wheel turning authority of the steering tiller and ended up inadvertently losing the grip of the nosewheel on the runway.

It will be interesting to see how this all shakes out.

Report cites steering in Denver jet crash

USA Today, January 8, 2009

The captain of a Continental Airlines jet that skidded off a Denver runway and burst into flames last month attempted to steer the jet using a method linked to runway accidents in the past, federal accident investigators reported Wednesday.

The National Transportation Safety Board has not said what caused Flight 1404, a Boeing 737-500 headed for Houston, to skid off the runway on Dec. 20 while attempting to take off in a brisk crosswind. But a preliminary report released by investigators offers the first glimpse of what might have triggered the crash.

All 115 people aboard escaped as jet fuel burned through the right side of the jet. The crash injured 38 people, five of whom were hospitalized, the NTSB said.

As the jet accelerated toward takeoff, the captain attempted to keep it rolling straight by turning the small pair of wheels under the jet's nose, the NTSB said the pilot told investigators. The nose gear is turned with a device called a tiller. The captain is not named in the report.

Two former accident investigators, Kevin Darcy and John Cox, who are not connected to the government's probe, said that using the tiller could cause the front tires to lose traction and start to skid. Pilots typically use the tiller to turn while taxiing at slow speeds, but once a jet accelerates, they steer with rudder pedals, they said.

Nose-wheel steering is something investigators will likely focus on, said Darcy, a former Boeing accident investigator who now works as a safety consultant. Darcy said he investigated a 737 accident in Mumbai in the 1990s which was partly blamed on the pilots' attempt to steer with the tiller during takeoff.

The NTSB cited "excessive nose-wheel steering" as part of the reason for a 1995 accident at John F. Kennedy International Airport involving a 747.

"It is unusual to need a tiller in a 737 on a runway, regardless of wind," said Cox, a former US Airways pilot who is also a safety consultant. "In all my years, I never needed the tiller. The rudder steering was always sufficient."

The winds at Denver were gusting up to 37 mph from the west as the jet attempted to take off to the north. Jets naturally tend to turn into the wind, just as a weather vane does. The Continental jet turned into the wind.

 

[Teller1900]

Additional info from an airline pilot, to supplement the article quoted below.

If you use the steering "tiller" to turn the nose wheel, you are not moving the rudder. The steering tiller gives you more left and right motion of the nose wheel than the rudder pedals, but past a certain point, depending on speed, the nose wheel will start skidding sideways and will lose the ability to turn the aircraft.

It's possible he was applying full rudder and felt he needed the extra nose-wheel turning authority of the steering tiller and ended up inadvertently losing the grip of the nosewheel on the runway.

It will be interesting to see how this all shakes out.

Our rudder pedals have 8 degrees of control authority (more than enough to make a high speed exit), either side of center. The tiller has an additional 70 degrees of authority (and the gear can caster to 110 degrees). I don't know how touchy the tiller is on a 737, but I've seen guys successfully use ours at high speed. As long as you're gentle with it, it's just another way of controlling the aircraft. I'll be interested to see what the NTSB says about this.

 

[sba55]

Our rudder pedals have 8 degrees of control authority (more than enough to make a high speed exit), either side of center. The tiller has an additional 70 degrees of authority (and the gear can caster to 110 degrees). I don't know how touchy the tiller is on a 737, but I've seen guys successfully use ours at high speed. As long as you're gentle with it, it's just another way of controlling the aircraft. I'll be interested to see what the NTSB says about this.

Obviously, I don't fly 737s, but I've heard from at least two former 737 captains that their OpsSpecs specifically forbade the use of the tiller once on the runway. They (John Deakin, for instance) made it seem like it wasn't a good idea to use it at high speeds.

-Felix

 

[Greg Bockelman]

Obviously, I don't fly 737s, but I've heard from at least two former 737 captains that their OpsSpecs specifically forbade the use of the tiller once on the runway. They (John Deakin, for instance) made it seem like it wasn't a good idea to use it at high speeds.

-Felix

I am not convinced yet that the tiller was the primary culprit. If the Captain touched the tiller at high speed, I would suspect that it was because the rudder steering wasn't keeping the airplane straight.

 

[AWACSEng]

SOP for us is to use nosewheel steering (tiller) untill the rudder becomes effective (~65 kts). After that the hand comes off the tiller and rudder only for the rest of the roll. In the event of the critical engine fails, the tiller may be used to supplement the rudder in maintaining a parallell track down the runway. However, only 5-7 degrees on steering is usefull. Any more than that and the nosewheels start to skid. If the runway is wet, nosewheel steering effectiveness is nil, so it is not touched. The only reason the tiller is used is because of the disrupted airflow over the rudder at slow speeds due to the rotodome.

And Greg, I agree with you. It would take more than steering input to depart the prepared surface. If anything, the nosewheels would have scrubbed and skidded if anything. We actually aborted a takeoff a few weeks ago because the pilot had full left tiller in and the airplance was sliding right of centerline on the takeoff roll. I was just waiting for the nosewheel to catch a dry spot on the runway.

 

[TMetzinger]

I am not convinced yet that the tiller was the primary culprit. If the Captain touched the tiller at high speed, I would suspect that it was because the rudder steering wasn't keeping the airplane straight.

The impression I got was that the tiller wasn't used until they were already pretty far into the runway and still drifting. My assumption from the report (so far) was that full rudder had already been used and the tiller was used to get some extra nosewheel deflection.

Now we can argue that it would be pointless to use the tiller at that point because the nosewheel deflection was already ineffective and the nosewheel may have been skidding or not in contact with the runway. But it brings to mind something I read once (maybe in "The Right Stuff"?):


"I've tried A! I've tried B! I've tried C! Give me something else I can try!"

I can't fault a captain for trying something else if/when all recommended procedures are ineffective.

 

[Greg Bockelman]

I can't fault a captain for trying something else if/when all recommended procedures are ineffective.

Exactly. Which goes to what I was saying. To say that use of the tiller was anything other than a contributing factor is way premature at this point. If they were using the tiller, it would have been because nothing else was working.

 

[RotorAndWing]

Obviously, I don't fly 737s, but I've heard from at least two former 737 captains that their OpsSpecs specifically forbade the use of the tiller once on the runway. They (John Deakin, for instance) made it seem like it wasn't a good idea to use it at high speeds.

-Felix

I would seriously doubt there is OpSpecs for tiller use. Use of aircraft controls fall under the AOM.

 

[RotorAndWing]

I am not convinced yet that the tiller was the primary culprit. If the Captain touched the tiller at high speed, I would suspect that it was because the rudder steering wasn't keeping the airplane straight.

Agreed. Use what you have to get the job done.

 

[Skip Miller]

Obviously, I don't fly 737s, but I've heard from at least two former 737 captains that their OpsSpecs specifically forbade the use of the tiller once on the runway and lined up. They (John Deakin, for instance) made it seem like it wasn't a good idea to use it at high speeds.

-Felix

There, fixed that for you!

-Skip

 

[RogerT]

Agreed. Use what you have to get the job done.

Okay .. I know nothing about flying a 737, but if the plane will fly off on
one engine past V1, in a situation like this why couldn't you use differential
power on the engines? In other words if the strong crosswind from the left
is keeping you from staying on centerline .. throttle back the right engine
slightly until right after liftoff.

RT

 

[bbchien]

Bad idea. Too much lag time to power generation.

 

[RogerT]

Bad idea. Too much lag time to power generation.

If the plane will fly off above V1 on one engine .. why would the time
to spool back to full power be an issue? And I'm assuming you wouldn't
have to come back to flight idle, just a reduction to assist in keeping it
straight.

 

[TMetzinger]

V1 is not the speed at which the airplane will fly, so to speak. It's the speed at which you commit to the takeoff, and the airplane is certified to continue to accelerate to rotation speed and fly at or above V2 (takeoff safety speed) with one engine inop and the other at some (probably max) power setting, BEFORE YOU RUN OUT OF RUNWAY and to meet a minimum climb gradient.

The V speeds are derived for predetermined power settings with both engines operating at those settings to at least the point where you reach V1.

Mess with the power settings and your Vspeed calcs go out the window, which might have you running off the end of the runway before reaching flying speed.

Jet Drivers, have I got this right? I think so, but since I don't live with it every day I may be misunderstanding it.

 

[Greg Bockelman]

V1 is not the speed at which the airplane will fly, so to speak. It's the speed at which you commit to the takeoff, and the airplane is certified to continue to accelerate to rotation speed and fly at or above V2 (takeoff safety speed) with one engine inop and the other at some (probably max) power setting, BEFORE YOU RUN OUT OF RUNWAY and to meet a minimum climb gradient.

That is pretty much it.

Mess with the power settings and your Vspeed calcs go out the window, which might have you running off the end of the runway before reaching flying speed.

That really only applies to V1. But a minor reduction on one engine to compensate for a crosswind isn't going to affect takeoff distance or V1 enough to really notice.

Jet Drivers, have I got this right?

Pretty much. :smile:

 

[flyingcheesehead]

V1 is not the speed at which the airplane will fly, so to speak. It's the speed at which you commit to the takeoff, and the airplane is certified to continue to accelerate to rotation speed and fly at or above V2 (takeoff safety speed) with one engine inop and the other at some (probably max) power setting, BEFORE YOU RUN OUT OF RUNWAY and to meet a minimum climb gradient.

The V speeds are derived for predetermined power settings with both engines operating at those settings to at least the point where you reach V1.

Mess with the power settings and your Vspeed calcs go out the window, which might have you running off the end of the runway before reaching flying speed.

Shouldn't be an issue. If you can't maintain directional control below V1, you abort. If you've already reached V1, you should be able to reduce power on one engine to any level all the way down to zero thrust and still make the takeoff.

No takeoff is so important that you should have to mess with power settings below V1 - Abort, try again (maybe on another day ).

Do we know yet whether CO1404 reached V1 prior to departing the runway? (I would think not.)

 

[TMetzinger]

Um... Good question, Kent. Like you, I don't know if V1 was reached, and at least when I did go through the ATOP sim program at UAL (where we did V1 cuts), we aborted for anything below 80, and bells and swerves above 80 but not at V1. The CO 737 manual I have (old, so may not reflect current practice) says the same thing.

Phrased another way, I think your question is:

"Did the crew of CO1414 comply with company policy regarding takeoff aborts"?

Not knowing current CO practices, I have no idea. It's possible the exit occurred during the abort, god knows we're talking about seconds here.

 

[Greg Bockelman]

Do we know yet whether CO1404 reached V1 prior to departing the runway? (I would think not.)

The numbers I have heard are 119 knots and I believe 132 knots. 119 is definitely below V1 and I am not sure what the 132 was in reference to. I think it was the max speed attained. It would have been close to V1, depending on the weight. Aprapo of nothing at all, V1 and Vr are the same on that model 737.

 

[Everskyward]

http://ntsb.gov/Publictn/2010/AAR1004.htm

PROBABLE CAUSE

The National Transportation Safety Board determines that the probable cause of this accident was the captain's cessation of right rudder input, which was needed to maintain directional control of the airplane, about 4 seconds before the excursion, when the airplane encountered a strong and gusty crosswind that exceeded the captain's training and experience.

Contributing to the accident were the following factors: 1) an air traffic control system that did not require or facilitate the dissemination of key, available wind information to the air traffic controllers and pilots; and 2) inadequate crosswind training in the airline industry due to deficient simulator wind gust modeling.