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Emirates tail strike

Old 09-13-2009, 12:05 PM
  #11  
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This really scares me that this error can have such dire consequences and as such, is crosschecked, triple crosschecked before proceding for takeoff. I'm surprised Emirates doesn't have a procedure to crosscheck the N1 setting during the takeofr roll.

As others have said, reduced power takeoffs are always used, unless maximum power the engines. Indirectly, they are used because they are safer. You are at a higher risk of having an engine failure at a higher thrust setting.

The industry is slowly changing the language surrounding these types of takeoffs. Imagine explaining to a lawyer that you were using a reduced power takeoff and you crashed into an obstacle or hit something on departure. That will go over like a fart in church.

Instead of using the words reduced power, those words are being replaced by the words alternate takeoff power. A full power rated takeoff is becoming a normal power takeoff. A bleeds off full power takeoff is becoming a Maximum Power Takeoff. You gotta love lawyers.
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Old 09-13-2009, 12:15 PM
  #12  
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Originally Posted by KC10 FATboy View Post
This really scares me that this error can have such dire consequences and as such, is crosschecked, triple crosschecked before proceding for takeoff. I'm surprised Emirates doesn't have a procedure to crosscheck the N1 setting during the takeofr roll.

As others have said, reduced power takeoffs are always used, unless maximum power the engines. Indirectly, they are used because they are safer. You are at a higher risk of having an engine failure at a higher thrust setting.

The industry is slowly changing the language surrounding these types of takeoffs. Imagine explaining to a lawyer that you were using a reduced power takeoff and you crashed into an obstacle or hit something on departure. That will go over like a fart in church.

Instead of using the words reduced power, those words are being replaced by the words alternate takeoff power. A full power rated takeoff is becoming a normal power takeoff. A bleeds off full power takeoff is becoming a Maximum Power Takeoff. You gotta love lawyers.
I can not agree that a reduced power takeoff is safer. The advantage of full power that might make a greater difference in a variety of situations vice a small chance of engine failure on take-off would seem to be playing the wroing side of the cards and ORM. I'm sure there are many differences in operating transport category aircraft than any others - but saying that you have a higher risk of engine failure at full thrust would then be a reason to apply this technique across all T/M/S of aircraft.

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Old 09-13-2009, 12:37 PM
  #13  
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USMCFLYR, I understand that you come from a community that enjoys afterburner takeoffs. Out of simplicity, you are given full mil or afterburner takeoff options.

Even in the military, we use reduced thrust takeoffs. An engine is statistically more likely to experience a failure at maximum power than at a reduced power setting. I don't have any source for that other that what was taught to me by Boeing during my FTUs.

During a reduced power takeoff, the aircraft must meet all of the same requirements as a normal power takeoff. If you lose an engine at Vcef/V1, you are still required to meet all performance requirements with the remaining engine(s) at the reduced thrust. In fact, in every aircraft I've flown with reduced thrust takeoffs, it was taught that you should not apply additional thrust (as it's always available to you) unless for some reason you need it.

I would MUCH rather fly an aircraft that has excess thrust available on takeoff, than an aircraft that needs maximum thrust available in order to get airborne.
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Old 09-13-2009, 01:03 PM
  #14  
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Originally Posted by KC10 FATboy View Post
USMCFLYR, I understand that you come from a community that enjoys afterburner takeoffs. Out of simplicity, you are given full mil or afterburner takeoff options.

Even in the military, we use reduced thrust takeoffs. An engine is statistically more likely to experience a failure at maximum power than at a reduced power setting. I don't have any source for that other that what was taught to me by Boeing during my FTUs.

During a reduced power takeoff, the aircraft must meet all of the same requirements as a normal power takeoff. If you lose an engine at Vcef/V1, you are still required to meet all performance requirements with the remaining engine(s) at the reduced thrust. In fact, in every aircraft I've flown with reduced thrust takeoffs, it was taught that you should not apply additional thrust (as it's always available to you) unless for some reason you need it.

I would MUCH rather fly an aircraft that has excess thrust available on takeoff, than an aircraft that needs maximum thrust available in order to get airborne.
Yes I do....and even though there are times when I would like to make a mil powered take-off (and maybe even a few times when I would make a mil powered take-off) we have to acknowledge that there is a significant safety factor that we are giving up. You've seen it on the video of cat shots even. The aircraft is NOT in A/B while in tension but halfway down the cat shot they engage the A/Bs - for that litttle extra safety margin; even though it is not required. I give it serious thought every time I do a section takeoff since I, as the lead, have pulled a couple of percent out of full A/B.

I understand that it seems to be common practice in the heavy transport community (military and civilian) to use reduced powered take-off per my earlier question and the responses received.

As far as statistical evidence that taking off at reduced thrust on the off chance of a engine failure at higher power vice the known safety margin that a full power provides (across all aircraft types), then I would have to say that IMO it is safer to use a full power takeoff. This would be an interesting safety study/discussion; but like you said - I have spent my entire career being taught that full power takeoffs are safer.

I am not familiar with the reduced pwer takeoff but I do understand what you mean when you say that aircraft must meet all of the performance requirements. I understand that they might JUST make those requirements (the mins), but that doesn't mean that it isn't safer to have a greater margin of making those minumums.

The earlier responses giving wear and tear as a reason for reduced power takeoffs seems right down the alley of the perserving the bottom line - the almighty dollar. In this instance - I believe it is a case of making a decision that a reduced powered takeoff saves gas, saves wear/tear, saves on noise and is GOOD ENOUGH to meet the safety requirements.

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Old 09-13-2009, 01:35 PM
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USMC,

"safer" does not mean the same thing in all situations, and is subjective.

It is a statistical FACT that a reduced power takeoff (turbofan engines) lowers the risk of engine failure. In that context, it is "safer."

Of course obstacle clearance and other things are factored in the equation to determine how much to reduce the takeoff thrust setting.

Also, at very light weight and aft CG configurations, 4-engine aircraft may become (temporarily) uncontrollable with an outboard engine failure during the takeoff roll. Hence another reason to use reduced power takeoffs.

In the fighter world, AB takeoffs are indeed "safer".
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Old 09-13-2009, 01:41 PM
  #16  
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You are comparing Naval Aviation catapult takeoffs with normal aviation takeoffs. Apples and oranges.

An engine is more likely to fail at higher power settings. This is a fact, and makes sense. The more power you ask from the engine, the more stress and heat damage you cause. If you are at a higher risk for using higher power settings, then why would you use them when you didn't need to?

This just isn't for heavies. The business jets, commuters, small airliners, and big jets use it.
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Old 09-13-2009, 01:51 PM
  #17  
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Originally Posted by navigatro View Post
USMC,

"safer" does not mean the same thing in all situations, and is subjective.

It is a statistical FACT that a reduced power takeoff (turbofan engines) lowers the risk of engine failure. In that context, it is "safer."

Of course obstacle clearance and other things are factored in the equation to determine how much to reduce the takeoff thrust setting.

Also, at very light weight and aft CG configurations, 4-engine aircraft may become (temporarily) uncontrollable with an outboard engine failure during the takeoff roll. Hence another reason to use reduced power takeoffs.

In the fighter world, AB takeoffs are indeed "safer".
Absolutely - which is why I am trying to understand the difference in what seem to be a heavy transport category aircraft procedure and one that fits across all type/model and series.

I have only flown light GA aircraft and the T-34C through Hornet in the military and I had never been introduced to reduced powered takeoffs. I would think that if it was safer to make reduced powered takeoffs because of high probability of engine failure vice the safety margin given a full power takeoff then it would seem that I might have come up against this technique sooner.

So...this seems to be a difference, so far at least since no one else from a different community has chimed in, to be a P121/heavy transport procedure.

Some of you seem to think that I am arguing against reduced powered takeoffs. to the contrary - having not flown P121 or heavy transport I don't know if it is better or worse. Just as I always do when sitting in the back I trust that the crews and procedures they are using have been vetted and found safe to operate.
I disagree with the contention that the small chance of an engine failure overrides the many safety margins that a full power takeoff gives you.
It gives me decreases takeoff distance, increased obsticle clearance, a steeper climb angle and getting me away from the ground quicker, and more thrust/speed should I have an emergency - which at least in my airplane and most others I have flown is a good thing.

Finally - though I have not seen it myself and even KC said that it was what was taught but has not seen the evidence - even if it was statistically a greater chance, my own Operational Risk Management says that I'll take the goods of a full power takeoff over the reduced power takeoff and the very small chance of engine failure due to a high power setting.

I wonder if given the oportunity - not goverened by your companies operating limitations (which are probably based on monetary savings or noise restrictions) - how many would CHOOSE a reduced powered takeoff?

Interesting discussion.

USMCFLYR

Btw - does anyone have any opinions on the failure of the double/triple checks of the numbers here? I've seen one post address this and that members procedure for backing up the numbers. What are some other techniques/procedures for ensuring good information in/good information out?
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Old 09-13-2009, 01:59 PM
  #18  
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Originally Posted by KC10 FATboy View Post
You are comparing Naval Aviation catapult takeoffs with normal aviation takeoffs. Apples and oranges.

An engine is more likely to fail at higher power settings. This is a fact, and makes sense. The more power you ask from the engine, the more stress and heat damage you cause. If you are at a higher risk for using higher power settings, then why would you use them when you didn't need to?

This just isn't for heavies. The business jets, commuters, small airliners, and big jets use it.
No KC - I was not comparing the takeoffs - rather the idea that I want every bit of thrust coming out of my engines that I can get. So far - this has been my thought process.

As for the second bolded comment - because just meeting the mins if I can have a higher safety margin is safer IMO.

I guess the problem I'm having in this discussion is the safety factor. I will have to do some research myself but I'd bet a beer that increase SAFETY is on down the list when the reasons for reduced power takeoffs are considered.

Navigatro
Also, at very light weight and aft CG configurations, 4-engine aircraft may become (temporarily) uncontrollable with an outboard engine failure during the takeoff roll. Hence another reason to use reduced power takeoffs.
This is a good point. I'm sure there are specific circumstances. Question for those flying the heavies - especially in the circumstances above - if on takeoff and let's say 500' - would the first procedure not be to go to full power on the remaining engines?

USMCFLYR

I'm sure it is used in all those situations that you mention.
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Old 09-13-2009, 02:11 PM
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Originally Posted by KC10 FATboy View Post
This really scares me that this error can have such dire consequences and as such, is crosschecked, triple crosschecked before proceding for takeoff. I'm surprised Emirates doesn't have a procedure to crosscheck the N1 setting during the takeofr roll.
If I remember correctly, besides a long duty day/fatigue, it was failure to crosscheck, or verify numbers that resulted in the ACMI 747 crash in YHZ a few years back.

I'd have to go through and reread the information, but I thought that's what main factors were.
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Old 09-13-2009, 02:12 PM
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Most military aircraft in the fighter/attack category have a fairly narrow operating weight range and would not benefit much from reduced thrust takeoffs. On some large jets the takeoff weight range can be up to around 50% of max gross. These jets also may keep an engine on the wing(no major overhaul) longer than a fighter's lifespan, so economy is an important and even vital requirement.
Reduced power takeoffs are not used if runway/aircraft conditions are critical. Safety is always the primary issue.

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"The general approach adopted by Boeing is the calculation of a Corrected Runway Length whichgeneralizes WAT-effects (Weight-Altitude-Temperature).The corrected Engine Inoperative Takeoff Distance is the actual runway length corrected for specificconditions such as the presence and use of a clearway, the effects of runway slope, wind, anti-ice,engine bleed, MEL-items, line-up distance, etc. The corrected Engine Inoperative Accelerate-Stop Distance is the actual runway length corrected forthe presence and use of a stopway, the effects of runway slope, wind, anti-ice, engine bleed, MEL-items, line-up distance, etc.The actual takeoff weight determines the takeoff safety speed V2 and the rotation speed VR isdetermined from V2 as a function of altitude and temperature.Whenever field length limited the maximum performance is obtained for the balanced takeoffwhere the corrected Engine Inoperative Takeoff Distance is equal to the corrected EngineInoperative Accelerate-Stop Distance, resulting in a balanced field length."
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Appendix 2: Takeoff Accidents resulting from inadequate performanceMK Airlines Limited Boeing 747-244SFOn 14 October 2004, an MK Airlines Limited Boeing 747-244SF was being operated as a non-scheduled international cargo flight from Halifax, Nova Scotia, to Zaragoza, Spain. At about 0654coordinated universal time, MK Airlines Limited Flight 1602 attempted to take off from Runway 24 atthe Halifax International Airport. The aircraft overshot the end of the runway for a distance of825 feet, became airborne for 325 feet and then struck an earthen berm. The aircraft's tail sectionbroke away from the fuselage, and the aircraft remained in the air for another 1200 feet before itstruck terrain and burst into flames. The aircraft was destroyed by impact forces and a severe post-crash fire. All seven crew members suffered fatal injuries.In this accident, the flight crew's take-off performance calculations resulted in an error thatremained undetected until the aircraft reached a point where the crew's response was too late toavert the accident.Source: Transportation Safety Board of Canada, Accident Report A04H0004Other Accidents; a review by the Transportation Safety Board of CanadaA review of large (above 5700 kg), turbine-powered aircraft accident and incident data has shownthat there have been at least 12 major occurrences where take-off performance was significantlydifferent from scheduled performance. Four of the aircraft involved were destroyed and there were297 fatalities.Several of these occurrences involved flight crews that attempted a take-off using incorrectperformance data, and then did not recognize the inadequate take-off performance of the aircraft.There were other accidents where the take-off performance has been inadequate because ofmechanical failures, incorrect aircraft configuration or incorrect instrument indications. Theseoccurrences were not isolated to any particular aircraft type, commercial operation or geographicarea.Underlying most of these occurrences were one or both of the following safety issues: The failure or absence of procedural defences to detect an error in the take-off performancedata; and The failure of the crews to recognize abnormal performance once the take-off hadcommenced. The following are some representative accidents taken from the data: On 12 March 2003, a Boeing 747-412 suffered a tail strike on take-off in Auckland, NewZealand, and became airborne just above the stall speed (New Zealand Investigation03 003). The aft pressure bulkhead was severely damaged, but the crew managed to landsafely. The cause of the tail strike was a result of the flight crew entering a take-off weight
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100 tonnes less than the actual weight into the flight management system, resulting in lowtake-off speeds being generated. There was no crew cross-checking of the speeds. On 11 March 2003, a Boeing 747-300 in Johannesburg had a tail strike on take-off (NTSBreport DCA03WA031 refers). The flight engineer had entered the zero fuel weight of203 580 kg instead of the take-off weight of 324 456 kg into the hand-held performancecomputer, and then transferred the incorrect computed take-off speeds onto the take-offcards. On 14 June 2002, an Airbus A330 had a tail strike on take-off in Frankfurt, Germany, becauseincorrect take-off data were entered into the flight management system (TSB reportA02F0069 refers). The tail strike was undetected by the flight crew, but they were notifiedby air traffic services during the climb-out. The aircraft sustained substantial structuraldamage to the underside of the tail. On 28 December 2001, a B747-200 cargo aircraft had a tail strike on take-off in Anchorage,Alaska, and sustained substantial damage (NTSB report ANC02LA008 refers). The crew didnot account for the weight of the additional fuel (about 45 360 kg) taken on board inAnchorage, and inadvertently used the same performance cards that were used for theprevious landing. The crew members were unaware that the tail had struck the runway untilafter arrival at their destination. On 13 January 1982, a Boeing 737-222 was on a scheduled flight from Washington, DC, toFort Lauderdale, Florida. During take-off, the EPRs were set for 2.04, and on the take-off run,anomalous engine instrument readings were noted; the captain elected to continue thetake-off. Approximately 2000 feet and 15 seconds past the normal take-off point, the aircraftbecame airborne. The aircraft initially climbed, but failed to accelerate. The stall warningstick shaker activated shortly after take-off and continued until the aircraft settled, hit the14th Street Bridge and several vehicles, then plunged into the frozen Potomac River. Theinvestigation revealed that the engine inlet pressure probes became blocked with ice,resulting in high EPR indications. Of the 79 persons on board, 74 perished, and there werefour ground fatalities. From at least as far back as 1972, there have been safety recommendations and initiatives to ensurethat crews have a reliable on-board method of detecting abnormal take-off performance,particularly in situations where performance is less than required or expected. Unfortunately, thereis still not a reliable in-cockpit system available for crews to detect and react to abnormal take-offperformance in a timely manner.Source: Transportation Safety Board of Canada
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