CNN: New caution for pilots landing on wet runways (thrust reversers)

[DeepModem Mom]

New caution for pilots landing on wet runways
Recommendation comes after plane overran runway and boy died
Friday, January 27, 2006


WASHINGTON (CNN) -- The National Transportation Safety Board is urging that commercial airplane pilots change the way they calculate stopping distances on slippery runways to avoid a crash, such as the one in Chicago that killed a child....

***

The NTSB wants the Federal Aviation Administration to prohibit airlines from calculating the effect of a plane's thrust reversers into the formula that figures what distance is needed to land when runways are slick.

The urgent recommendation comes from an NTSB investigation into what caused a Southwest Airlines flight, landing at Midway Airport in a snowstorm on December 8, to roll off the end of the runway -- where it tore through two fences and stopped in an intersection, hitting two cars. A 6-year-old boy in one of the cars was killed.

The pilots had used a laptop computer to calculate how far the plane needed to go to land, the NTSB said. When the runway's condition was entered as "wet-poor," the computer calculated they would be able to stop with 30 feet to spare.

But the calculations took into consideration that engine thrust reversers would be deployed at touchdown. Instead, the NTSB said, "flight data recorder information revealed that the thrust reversers were not deployed until 18 seconds after touchdown, at which point there was only about 1,000 feet of usable runway remaining."...


http://www.cnn.com/2006/TRAVEL/01/27/airplane.landings/index.html

[democrank]

1. Pilots on wet runways

is a welcome relief from shark attack warnings.

[DeepModem Mom]

3. LOL! Well, the story wasn't overplayed on the air --

and I think we have some pilots here at DU. I thought they might be interested.

[trotsky]

2. I don't think I've ever been on a plane

that deployed reverse thrusters immediately upon touchdown. They have all landed, coasted for a several seconds, then only when the plane was stable and fully on the ground were they activated.

So I question the wisdom of whoever wrote software that would assume reverse thrusters from the instant the plane touches the ground.

[0007]

4. I know I haven and I've been flying since the jet engine.

[nookiemonster]

5. I question that decision also.

Stability is paramount. The "clam shells" should only be activated by pilot interaction. Reversers divert ALOT of thrust in the opposite direction!! That in itself, should create a good visual, especially in crappy weather.

:)

[Poll_Blind]

6. In my experience, the usually deploy in the first 5 seconds...

...after touchdown. Eighteen seconds seems more than a bit long, unless there was a crosswind or something else which caused them to doubt their stability or orientation on the runway.

I agree, heartily, that whomever assumed that the reverse thrusters would be deployed instantly was not using the tools correctly and figuring in real-world numbers.

PB

[karlrschneider]

8. 5 seconds is probably a fair average....they will not deploy even if com-

manded to unless the 'squat' switches (detect that there is a significant percentage of the plane's weight on the landing gear) are closed. But of course like any mechanism they are subject to occasional though rare failure. I know of one case where the pilot(s?) pulled the levers back before touchdown figuring the safety switches would prevent reversal before the plane was (more or less) safely on the runway but one of them malfunctioned and immediately opened the clamshells on one engine...fortunately for them it was a 727 and it was the #2 (center) engine. If it had happened on a plane with wing-mounted engines it almost surely would have tossed it over into the south 40 immediately.

[fshrink]

9. You reverse when the aircraft is at or below

the stall speed all flaps out which means that the lift is close to 0. And of course you're 3 points on the ground. Now, reverse uses fuel and is more costly than brakes...

[karlrschneider]

7. This "story" is chock full of misinformation.

The very last sentence is close to right but not quite...landing distances are NEVER calculated using reversers as part of the formula. And "30 feet to spare"?? Utter nonsense...there is no way to arrive at such a figure.
Also, as is vaguely stated, the NTSB has no mandate, order or authority to tell pilots how to operate their aircraft. That is the FAA's responsibility (not that they're anywhere near perfect but it is -their- bailiwick, not NTSBs.)