BA 747 crew commended for escaping near-stall on take-off

[Whine Lover]

1st warning.

Do NOT discuss East/West issues in anything but an East/West thread. Period.

The next infraction results in a suspension for 7 days.

/mod

That's what I'm talkin' bout....

 

[avbug]

Would imagine it would be difficult to obtain certification if the aircraft was NOT flyable with 3 good engines and one in reverse... but thanks for asking. :/

So you really have no idea, and are applying guesswork. Got it.

Which segment climb gradient criterion applies three engines with one in reverse?

Boeing certifies to Part 25. The certification standard for the 747-400 is Part 25, reference the Type Certificate Data Sheet: http://www.airweb.faa.gov/Regulator...B53BDC83FBC4DA6E862576B1007071F4?OpenDocument

In which part of 14 CFR 25.121 do you find a requirement to climb on three engines with a fourth in reverse, to meet certification standards?

§ 25.121 Climb: One-engine-inoperative.

(a) Takeoff; landing gear extended. In the critical takeoff configuration existing along the flight path (between the points at which the airplane reaches V LOFand at which the landing gear is fully retracted) and in the configuration used in §25.111 but without ground effect, the steady gradient of climb must be positive for two-engine airplanes, and not less than 0.3 percent for three-engine airplanes or 0.5 percent for four-engine airplanes, at V LOFand with—
(1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with §25.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted; and
(2) The weight equal to the weight existing when retraction of the landing gear is begun, determined under §25.111.
(b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in §25.111 but without ground effect:
(1) The steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four-engine airplanes, at V2with:
(i) The critical engine inoperative, the remaining engines at the takeoff power or thrust available at the time the landing gear is fully retracted, determined under §25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the airplane reaches a height of 400 feet above the takeoff surface; and
(ii) The weight equal to the weight existing when the airplane's landing gear is fully retracted, determined under §25.111.
(2) The requirements of paragraph (b)(1) of this section must be met:
(i) In non-icing conditions; and
(ii) In icing conditions with the takeoff ice accretion defined in appendix C, if in the configuration of §25.121(b) with the takeoff ice accretion:
(A) The stall speed at maximum takeoff weight exceeds that in non-icing conditions by more than the greater of 3 knots CAS or 3 percent of VSR; or
(B) The degradation of the gradient of climb determined in accordance with §25.121(b) is greater than one-half of the applicable actual-to-net takeoff flight path gradient reduction defined in §25.115(b).
(c) Final takeoff. In the en route configuration at the end of the takeoff path determined in accordance with §25.111:
(1) The steady gradient of climb may not be less than 1.2 percent for two-engine airplanes, 1.5 percent for three-engine airplanes, and 1.7 percent for four-engine airplanes, at VFTOwith—
(i) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and
(ii) The weight equal to the weight existing at the end of the takeoff path, determined under §25.111.
(2) The requirements of paragraph (c)(1) of this section must be met:
(i) In non-icing conditions; and
(ii) In icing conditions with the final takeoff ice accretion defined in appendix C, if in the configuration of §25.121(b) with the takeoff ice accretion:
(A) The stall speed at maximum takeoff weight exceeds that in non-icing conditions by more than the greater of 3 knots CAS or 3 percent of VSR; or
(B) The degradation of the gradient of climb determined in accordance with §25.121(b) is greater than one-half of the applicable actual-to-net takeoff flight path gradient reduction defined in §25.115(b).
(d) Approach. In a configuration corresponding to the normal all-engines-operating procedure in which VSRfor this configuration does not exceed 110 percent of the VSRfor the related all-engines-operating landing configuration:
(1) The steady gradient of climb may not be less than 2.1 percent for two-engine airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for four-engine airplanes, with—
(i) The critical engine inoperative, the remaining engines at the go-around power or thrust setting;
(ii) The maximum landing weight;
(iii) A climb speed established in connection with normal landing procedures, but not exceeding 1.4 VSR; and
(iv) Landing gear retracted.
(2) The requirements of paragraph (d)(1) of this section must be met:
(i) In non-icing conditions; and
(ii) In icing conditions with the approach ice accretion defined in appendix C. The climb speed selected for non-icing conditions may be used if the climb speed for icing conditions, computed in accordance with paragraph (d)(1)(iii) of this section, does not exceed that for non-icing conditions by more than the greater of 3 knots CAS or 3 percent.

Whereas Boeing didn't find a requirement to use a snatch-back system for the thrust lever in the event of an unplanned thrust reverser deployment, an automatic stow system is in use and the need to demonstrate or certify climb with one in reverse was and is irrelevant. Boeing provides that one can either shut it down with the fuel control if it's a problem, or ignore it and fly, if it's not.

No assumption required.

§ 25.933 Reversing systems.

(a) For turbojet reversing systems—
(1) Each system intended for ground operation only must be designed so that during any reversal in flight the engine will produce no more than flight idle thrust. In addition, it must be shown by analysis or test, or both, that—
(i) Each operable reverser can be restored to the forward thrust position; and
(ii) The airplane is capable of continued safe flight and landing under any possible position of the thrust reverser.
(2) Each system intended for inflight use must be designed so that no unsafe condition will result during normal operation of the system, or from any failure (or reasonably likely combination of failures) of the reversing system, under any anticipated condition of operation of the airplane including ground operation. Failure of structural elements need not be considered if the probability of this kind of failure is extremely remote.
(3) Each system must have means to prevent the engine from producing more than idle thrust when the reversing system malfunctions, except that it may produce any greater forward thrust that is shown to allow directional control to be maintained, with aerodynamic means alone, under the most critical reversing condition expected in operation.

25.993 provides a requirement that either the reverser not affect the flight, or the flight be able to continue with the reverser deployed. The system must be designed such that if the reverser deploys, no more than idle thrust will be produced. The airplane was never required to have a system to auto-retard the thrust lever in the event of an unintended deployment.

 

[Lear70]

So, as I said, it can. Thanks for the long post basically saying so.

 

[avbug]

Actually, no. You made statements in error, namely regarding a system to retard the throttle, and then made statements in error that Boeing certified the airplane to fly with one engine producing reverse thrust. Neither is true.

14 CFR 25.933 provides that:

a. If the system does reverse in flight, it can't produce more than idle thrust

b. a malfunctioning reverser has a means of restoring forward acting thrust

c. the airplane may be continued safely and landed under any possible position of the reverser. This does NOT imply that the engine must be producing thrust. This refers only to the physical position of the reverser...not to an engine producing reverse thrust, even idle reverse thrust. To meet this requirement, the engine may be shut down.

 

[Lear70]

In your attention to minutia, as always, you miss the forest for the trees.

I said I *believed* the throttle would automatically retard to idle, but that I wasn't sure. Thanks for the clarification on that detail.

The POINT, however, was my certainty that the aircraft was perfectly flyable with one engine at reverse idle and the rest developing takeoff thrust. While your detailed analysis doesn't "imply" that an engine stuck in reverse is, in fact, still at idle, before it can be shut down, the simple FACT is that, in ANY aircraft with more than 2 engines, it takes a moment to identify which engine is faulty, confirm it, and shut it down.

I have flown aircraft with "auto-stow" features in the reverser logic and, the simple fact of the matter is, they don't always work. In a takeoff scenario where I had elected to continue the takeoff roll, I likely wouldn't be trying to figure out which one it was until AFTER breaking ground, the gear is up, and a positive rate of climb is established at target speed (some reverser deployed memory items on some aircraft are accomplished before minimum safe altitude, but always after the aircraft is at least climbing and stabilized in a climb attitude and airspeed).

So yes, you confirmed my assumption. No, nothing you've said before or after changes that basic assumption. Happy Independence Day.

 

[bubbers44]

My friend, who obviously was a very good pilot, had the right engine of a 727 go into reverse on take off in MIA. The engines remained at TO power on that engine while he was sorting out why the FO couldn't hold runway heading after takeoff. He assumed control to see why they were barely climbing and couldn't stay on runway heading with full rudder without using bank also. No indications in cockpit because only the outboard reverser of the engine failed in reverse. He found by bringing back the right engine to idle they could climb and return for landing. Boeing said they had never had it happen before. ******************** happens so don't totally rely on a checklist to get you back alive.

 

[Magichands]

Great job guys! Way to keep cool under extreme pressure. You guys are a credit to the profession.

 

[igneousy2]

Great job BA!

As far as rejecting...a reject at over 120 knots in a 747 is a BIG deal. 14,000 feet is not a lot of runway if you are hot and/or high enough as it seems this airport was.

A high speed reject in a 747 is an EMERGENCY. Having a reverser unlock light illuminate without any other indication of a problem is an abnormal.

Even knowing everything I bet the Captain of this airplane would rather have to deal with some retracted slats on takeoff then reject at high speed.

A reject in a 747 and a CRJ are not even in the same league.

 

[waveflyer]

Actually, no. You made statements in error, namely regarding a system to retard the throttle, and then made statements in error that Boeing certified the airplane to fly with one engine producing reverse thrust. Neither is true.

14 CFR 25.933 provides that:

a. If the system does reverse in flight, it can't produce more than idle thrust

b. a malfunctioning reverser has a means of restoring forward acting thrust

c. the airplane may be continued safely and landed under any possible position of the reverser. This does NOT imply that the engine must be producing thrust. This refers only to the physical position of the reverser...not to an engine producing reverse thrust, even idle reverse thrust. To meet this requirement, the engine may be shut down.

somebody's got check airman disease.

 

[SFR]

http://www.flightglobal.com/article...nded-for-escaping-near-stall-on-take-off.html


Instead of following the typical climb profile, the first officer - whose aerobatic experience meant he was familiar with buffet - .

Good job crew! I am just not sure what being familiar with Jimmy Buffet has to do with this incident???? Why would the author bring that up???