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Watch your jetblast

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Watch your jetblast

Old 7th Jul 2016, 18:57
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Watch your jetblast

A Lufthansa Boeing 747-800, registration D-ABYJ performing flight LH-403 from Newark,NJ (USA) to Frankfurt/Main (Germany), had safely landed on Frankfurt's runway 25L and was taxiing to its gate C15 via taxiway N. While turning left off taxiway N onto gate C15 the engine exhaust gasses hit two airport busses serving another aircraft at parking position V129 and caused a number of bus windows to shatter. Flying splinters of glass injured one of the 70 passengers on one of the busses.

On Dec 4th 2015 Germany's BFU reported in their August bulletin that according to the flight data recorder the aircraft's speed reduced from 5 to 1 knot while turning left into the gate, the #4 engine accelerated to 50% N1 with engine #1 remaining at 40%, engine #2 at 0% and engine #3 at 43% N1. The aircraft's speed increased to 7 knots afterwards.

The first bus received a shattered window on the right hand side between front and middle door, the left hand engine cover at the rear of the bus was torn away. The second bus received two shattered windows at the left hand rear of the bus, the splinters exited the bus through the opened right hand aft door and were distributed all over stand V129. The flying splinter caused a minor facial injury to one of the 70 passengers aboard that second bus.

The BFU reported that the airline stated in their operations manual: "[Ö] Idle thrust is adequate for taxiing under most conditions. A slightly higher thrust setting is required to begin taxiing. [Ö] Breakaway power should be limited to 40% N1!" In another section of the operations manual it is written: "One or two engine(s) should be shutdown for environmental reasons and fuel saving, taking into account condition of taxiways and ramps (i.e. upslope, icing etc.). [Ö] Two engines out taxi-in permitted if all conditions are favorable (e.g. weight, taxi route, weather)."

On Jul 4th 2016 the BFU concluded their investigation with their factual report without conclusions or analysis.
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Old 7th Jul 2016, 19:10
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Idle N1 on the 747-8/GEnx is ~21% - several percent lower than the idle N1 for the 747-400 PW4000 or CF6 installations (~25% N1). 40%-50% N1 sounds extremely high for taxi.
Some 747 pilots will push the outboard engine up a bit to help rotate the aircraft in a turn, but even then over 40% N1 sounds excessive.
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Old 7th Jul 2016, 19:33
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I blame the busses not the flight crew. The road traffic there drive like maniacs cutting close in front of taxiing aircraft, and obviously far too close behind!
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Old 7th Jul 2016, 20:27
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Maybe a footnote to avherald where you copied this from would be appropriate?

In any case, the entire thread should clearly be moved to JetBlast.
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Old 7th Jul 2016, 20:30
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Right. So you have two busses parked and decanting passengers onto an aircraft parked across the taxiway, when a 747 swings into a stand on the other side, runs out of momentum and gives it a bootfull. And the broken windows resulting from that, is the fault of the bus drivers exactly how?
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Old 7th Jul 2016, 21:02
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Rules rules ????

or is this at the discretion of the pilot the same as in-flight?

I always thought that all vehicles had to give way to a manuevering plane.

At any rate does this come under occupational hazards or a violation of air regulations?.

If it's the former it best fits somewhere else like Jet Blast
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Old 7th Jul 2016, 21:36
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Why do you think that sub-forum on here is named 'Jet Blast'?
"Errors have been made, others will be blamed".
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Old 7th Jul 2016, 22:16
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While we don't know all the specifics here, we do know some. Adding thrust on all 4 engines evenly would likely result in a lesser speed of jetblast required to move the aircraft, Differential thrust is likely not necessary. If possible, approaching the gate at about 10 knots(if possible) will reduce the likelyhood of the aircraft getting as slow as it did(1 knot).
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Old 8th Jul 2016, 02:36
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A Virgin Aust. FO was seriously injured when the competition's 747 got upto 45% N1 taxiing at Brisbane and blew over the stairs he was standing on.


Surprised the recent event was enough to blow out glass windows though.
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Old 8th Jul 2016, 07:20
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On Jul 4th 2016 the BFU concluded their investigation with their factual report without conclusions or analysis.
Am I the only surprised that the BFU elected not to make any recommendations further to this? Is this "routine" and acceptable event at FRA?
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Old 8th Jul 2016, 08:19
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They obviously need stronger buses!

I think this kind of incident is going to happen every now and then, just due to statistical likelihood. All the holes lined up: environmental conditions, positions of the buses and aircraft, power settings, etc. Change any one of those and it wouldnít have happened.

I notice that one of the engines was at 0%. Itís SOP to shut down an engine if you can where I work, unless there are good reasons not to. Personally, I keep them all running unless I can manoeuvre onto stand without increasing power in the turn (777). Itís not just windows on buses, imagine what could happen if an empty cargo container got hefted across the apron - it could easily kill people. The amount of junk that gets left around the edges of parking areas makes this kind of thing a distinct possibility at many airports...
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Old 8th Jul 2016, 09:38
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I remember watching a BA 777 self manouevering onto a remote stand at PMI to park nose out. It ran out of steam in the turn so the outside engine thrust was increased, but to such a high setting that all the adjacent taxiway signage was blown away and across the other side of the taxiway
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Old 8th Jul 2016, 09:43
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imagine what could happen if an empty cargo container got hefted across the apron - it could easily kill people.
That exact incident happened at my company about 5 years ago.

777F landed at PANC, was given a gate requiring two right turns. They shut down the right engine after cooldown.

After that, gate was changed and new gate required a right and then two lefts. Captain attempted to do it on the left engine... last turn was slightly uphill as well. Jet blast caught an empty cargo container and launched it onto a ramp worker sitting on a tug. Broke damn near every bone in his body.

Less-than-all-engine-taxi is a great idea, until it ain't. And the blame will lie squarely on the captain's shoulders.
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Old 8th Jul 2016, 10:07
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Less-than-all-engine-taxi is a great idea, until it ain't. And the blame will lie squarely on the captain's shoulders.
Thatís one of the reasons why Iím a bit cagey about doing it sometimes, quite apart from the fact that I donít want to injure anyone. In some of the countries I fly to, the FCOM is not going to get you out of jail...
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Old 8th Jul 2016, 10:28
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Surprised the recent event was enough to blow out glass windows though.
Its the little stones/gravel picked up in the blast that shatter the window, then the pressure pushes it through. Don't ask me how i know.
You can shatter a car window in an emergency (or nefariously) with a handful of gravel thrown at it.

Last edited by hoss183; 8th Jul 2016 at 10:29. Reason: typo
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