Take off alternate - Landing distance req
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Take off alternate - Landing distance req
We all agree that prior to departure, a pilot need to confirm that for the destination and alternate aerodromes is he able to meet the regulatory requirement, which means lands within 60% of the LDA.
What about a take off alternate? do we need to comply with the certified data (regulatory req) or can we use the operational (advisory) data?
Looking at EASA, it is said all alternate so it includes the take off alternate.
But for a take off alternate I would guess you would look at the One engine out performance which is by definition an advisory data. But if we need to look at a dispatch calculation for the take off alternate we would then have to multiply this by 1,67 in dry condition ?
thanks for your thought.
What about a take off alternate? do we need to comply with the certified data (regulatory req) or can we use the operational (advisory) data?
Looking at EASA, it is said all alternate so it includes the take off alternate.
But for a take off alternate I would guess you would look at the One engine out performance which is by definition an advisory data. But if we need to look at a dispatch calculation for the take off alternate we would then have to multiply this by 1,67 in dry condition ?
thanks for your thought.
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Why would you look at the one engine performance ? There are multitude of different reasons why you might need to return. For example our aircraft are approved for a planned full Cat 3b 75m with single engine. It is far more likely to need to return for a non engine related problem. If you need to return for any reason and the weather prevents it then you need a take off alternate. You may well return overweight or have electrical or hydraulic problems. The regulations only require you to dispatch with 1.67/1.92 for the destination and its related alternate as its presumed you will be at normal weights on arrival. That's why this requirement is in the landing section of the regulations not the take off section. A turn back to a take off alternate must therefore be assumed to be an enroute diversion and as such requires no factor for a non normal. The newest Performance tools will however include 15% for an enroute landing with no non normal.
Last edited by 8che; 22nd Dec 2015 at 21:04.
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KISS guys...
Choose an aerodrome that is familiar with your ops., and you know has sufficient LDA. calculating this and that before the flight...come on!
Much more important to find a filed where the weather is going to be benign than worry about 1.67 etc.
Choose an aerodrome that is familiar with your ops., and you know has sufficient LDA. calculating this and that before the flight...come on!
Much more important to find a filed where the weather is going to be benign than worry about 1.67 etc.
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just read that again Nick....where is the requirement to check one engine landing performance ? What you refer to defines the maximum distance to the alternate. Nothing else and they should be set numbers in your companies OPS SPEC that goes into your PART A. The requirement for a take off alternate is simply weather and nothing to do with the reason for the return. Instead of just reading regulations think about the reasoning behind them. An engine failure requires land at the nearest suitable airport which is why distance is important.
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And hence the requirement to ensure your LDA is sufficient for the OEI scenario.
I'm ready to be wrong but as I read that regulation and the stipulations further down there seems to be a requirement to ensure you can land?
I'm ready to be wrong but as I read that regulation and the stipulations further down there seems to be a requirement to ensure you can land?
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8che,
unfortunately our aircraft are not catIIIb and as such cannot perform CAT III one engine out.
Yes you can have multiple scenario but the take off alternate is chosen to be within one hour one engine LRC. If you have an hyd problem, electrical problem you can still fly on 2 engine and as such will cover more ground that on one engine.
An enroute airport is still called alternate as per Air Ops and as such during dispatch you would still need to cover for the dispatch criteria either 1,67 or 1,92.
While I agree the take off alternate is mostly due to weather, landing on engine would be worst scenario as you need to land at the nearest suitable airport. You would not spend time lowering the fuel before landing. If you had flight control or gear problem, you would fly more longer as to reduce your landing weight by burning fuel (and such cover more ground to a suitable alternate)
But whatever scenario you take, the question was do we need to consider dispatch criteria or not. Looking at Air Ops and the reply from B737900Er, it is an alternate and as such you need to use those rules.
unfortunately our aircraft are not catIIIb and as such cannot perform CAT III one engine out.
Yes you can have multiple scenario but the take off alternate is chosen to be within one hour one engine LRC. If you have an hyd problem, electrical problem you can still fly on 2 engine and as such will cover more ground that on one engine.
An enroute airport is still called alternate as per Air Ops and as such during dispatch you would still need to cover for the dispatch criteria either 1,67 or 1,92.
While I agree the take off alternate is mostly due to weather, landing on engine would be worst scenario as you need to land at the nearest suitable airport. You would not spend time lowering the fuel before landing. If you had flight control or gear problem, you would fly more longer as to reduce your landing weight by burning fuel (and such cover more ground to a suitable alternate)
But whatever scenario you take, the question was do we need to consider dispatch criteria or not. Looking at Air Ops and the reply from B737900Er, it is an alternate and as such you need to use those rules.
Folks,
As an old and far from bold pilot, with around 50 years in the business, such discussions as this really concern me!!.
All quasi-legalistic and ignores the real world, lulled into a very false sense of security because modern aircraft are so reliable, and serious non-normal situations may never be experienced by a pilot in a career --- outside of the sim.
And, believe me, real world emergencies never run like a sim. exercise --- that is when you find your personal proof of Murphie's Law.
The whole reason for "factoring" was/is because the "average" pilot cannot achieve the un-factored distances in the real world.
Not even close!!
So, if you commit yourself to a landing, and you have only the raw distance available, you are going to go off the end ---- and reverse thrust, which is not accounted for, is not going to save you.
If it is a "do or die" exercise, an uncontrollably fire, or minutes of fuel remaining, or some such dire situation, where running of the end is the least of your worries, so be it.
But for most situation, remember you are not a test pilot flying under test condition. So don't plan to be!!
Personally, I do not care what might be "legally" permitted, what phase of flight it might be, from pre-flight briefing to beer o'clock, except in extremis, as PIC I will want "real world" runway lengths available, 1.67 is good, more is better.
Tootle pip!!
PS: As my Christmas T-shirt says:"Common sense is now so uncommon, it should be re-classified as a superpower"
As an old and far from bold pilot, with around 50 years in the business, such discussions as this really concern me!!.
All quasi-legalistic and ignores the real world, lulled into a very false sense of security because modern aircraft are so reliable, and serious non-normal situations may never be experienced by a pilot in a career --- outside of the sim.
And, believe me, real world emergencies never run like a sim. exercise --- that is when you find your personal proof of Murphie's Law.
The whole reason for "factoring" was/is because the "average" pilot cannot achieve the un-factored distances in the real world.
Not even close!!
So, if you commit yourself to a landing, and you have only the raw distance available, you are going to go off the end ---- and reverse thrust, which is not accounted for, is not going to save you.
If it is a "do or die" exercise, an uncontrollably fire, or minutes of fuel remaining, or some such dire situation, where running of the end is the least of your worries, so be it.
But for most situation, remember you are not a test pilot flying under test condition. So don't plan to be!!
Personally, I do not care what might be "legally" permitted, what phase of flight it might be, from pre-flight briefing to beer o'clock, except in extremis, as PIC I will want "real world" runway lengths available, 1.67 is good, more is better.
Tootle pip!!
PS: As my Christmas T-shirt says:"Common sense is now so uncommon, it should be re-classified as a superpower"
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An engine failure requires land at the nearest suitable airport which is why distance is important.
I'd always thought that takeoff altn' within 60mins was for the 'land at nearest suitable' and that can be for more than an engine failure on a 'twin'. (remember the 3 engine flight on a 4 donk a/c much debated on here) In a twin, if you are non-ETPS, do you not need to remain within 1hr of a suitable airfield. Is this not where the 60min rule comes from? In the event of other systems failure one might consider an airfield, even destination, as most suitable.
A non engine related problem might be departing with APU u/s and then losing another source of AC = 1 source only.
I'd always thought that takeoff altn' within 60mins was for the 'land at nearest suitable' and that can be for more than an engine failure on a 'twin'. (remember the 3 engine flight on a 4 donk a/c much debated on here) In a twin, if you are non-ETPS, do you not need to remain within 1hr of a suitable airfield. Is this not where the 60min rule comes from? In the event of other systems failure one might consider an airfield, even destination, as most suitable.
A non engine related problem might be departing with APU u/s and then losing another source of AC = 1 source only.
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How About NOT Flying?
@LedSled came close, others noted that these events are most often weather related. WFT guys? If the weather at your departure point is so bad that you cannot return, whether on one engine or two, perhaps a better answer is to keep the SOB on the ground. Regardless of aircraft type, a cute little yellow Piper or the monster A380, if you don't like the weather, Do Not Fly! IIRC, that subject was addressed during Day ONE of my ground training many decades ago. 
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No Fly Zone,
Sems you are not working for an airline... Guess I'd like to see the face of your Chief Pilot or Director of Flight Ops if you call them "Guys wx is **** I'm not flying" while you could you have gone in accordance with the law.
Yeah I agree common sense is gone from a big part of the aviation community. But the law and regulation is something we can stick to it and as a Pilot, something I need to know and abide. Then you have common sense and airmanship.
But frankly, nowadays, my common sense is telling me to get a different job where we are at least considered a bit ! Now a pilot is just a glorify train driver and that's what my common sense is telling me ...
Sems you are not working for an airline... Guess I'd like to see the face of your Chief Pilot or Director of Flight Ops if you call them "Guys wx is **** I'm not flying" while you could you have gone in accordance with the law.
Yeah I agree common sense is gone from a big part of the aviation community. But the law and regulation is something we can stick to it and as a Pilot, something I need to know and abide. Then you have common sense and airmanship.
But frankly, nowadays, my common sense is telling me to get a different job where we are at least considered a bit ! Now a pilot is just a glorify train driver and that's what my common sense is telling me ...
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Yes Nick you must be able to land. The point is you don't need 1.92 or 1.67 to do it.....just like every airfield you pass over within 1 hours flying distance when you go on your flight. The T/O alternate is no different you need to land ASAP hence the distance rule (not a performance rule) if you cannot return to departure airfield.
The clue is in the word DISPATCH. Dispatch requires all the regulatory extra bits and pieces..... but you cannot dispatch an engine failure. That's why you wont find any S/E performance with a factor in a QRH or OPT (Boeing) because that's all classed as ENROUTE performance. The regulator does not ask the manufacturer to produce this data so it doesn't exist. Knowing this are you seriously suggesting someone is regulatory required to get the back of a cigarette packet out and start adjusting the data to artificially increase the landing data for a T/O alternate because the incredibly expensive OPT/AFM software isn't correct ?
The clue is in the word DISPATCH. Dispatch requires all the regulatory extra bits and pieces..... but you cannot dispatch an engine failure. That's why you wont find any S/E performance with a factor in a QRH or OPT (Boeing) because that's all classed as ENROUTE performance. The regulator does not ask the manufacturer to produce this data so it doesn't exist. Knowing this are you seriously suggesting someone is regulatory required to get the back of a cigarette packet out and start adjusting the data to artificially increase the landing data for a T/O alternate because the incredibly expensive OPT/AFM software isn't correct ?
Sir737,
I worked for an airline (and a bloody good one) for 35 years, including Check and Training on Boeing heavy metal.
For those of you who cannot read, I say again: The factors are there because the average line pilot, flying the average line aeroplane, has no/nil/nada/zilch chance of producing anything like the unfactored results achieved in certification test flying. With very rare exceptions, you have never been trained in or demonstrated your competence in the specialized techniques used. How many of you even know, theoretically, what comprises those techniques.
To seriously suggest you can demonstrate them, to the test standard, in an emergency diversion, is delusional.
This factoring all came about (as did most certification airfield performence requirements) from hard won experience.
Take "1.92" ---- this is the factored length under FAR 25 + 15% = 1.92 of the raw test figures, for a wet runway ---- the 15% being (last time I noticed, a recommendation) because some aircraft didn't stop in the full factored distance.
This has become such a screw-up in Australia, that we had certain CASA FOIs (with nil experience on heavy aircraft, let alone any serious knowledge of certification standards) wanting the factored dry field length multiplied by a further 1.92 if the runway was wet. This left only three runways in the whole of Australia where you could land a Citation Mustang, if the runway was wet.
Tootle pip!!
I worked for an airline (and a bloody good one) for 35 years, including Check and Training on Boeing heavy metal.
For those of you who cannot read, I say again: The factors are there because the average line pilot, flying the average line aeroplane, has no/nil/nada/zilch chance of producing anything like the unfactored results achieved in certification test flying. With very rare exceptions, you have never been trained in or demonstrated your competence in the specialized techniques used. How many of you even know, theoretically, what comprises those techniques.
To seriously suggest you can demonstrate them, to the test standard, in an emergency diversion, is delusional.
This factoring all came about (as did most certification airfield performence requirements) from hard won experience.
Take "1.92" ---- this is the factored length under FAR 25 + 15% = 1.92 of the raw test figures, for a wet runway ---- the 15% being (last time I noticed, a recommendation) because some aircraft didn't stop in the full factored distance.
This has become such a screw-up in Australia, that we had certain CASA FOIs (with nil experience on heavy aircraft, let alone any serious knowledge of certification standards) wanting the factored dry field length multiplied by a further 1.92 if the runway was wet. This left only three runways in the whole of Australia where you could land a Citation Mustang, if the runway was wet.
Tootle pip!!
8che,
Please re-read my posts, I made no specific reference to engine out condition, just the impossibility of any of us achieving the raw unfactored figures. Believe me, I have gone close, taking a B707-321C into Lasham.
As to engine-out field lengths (if any) --- any idea where they (or any "data" for other non-normal approach conditions) might come from??
As to what is manufacturer's "certified" data in an aeroplane performance manual -- that is a whole other can of worms, where those who have never bothered to acquaint them selves with the facts argue their misconceptions.
Tootle pip!!
Please re-read my posts, I made no specific reference to engine out condition, just the impossibility of any of us achieving the raw unfactored figures. Believe me, I have gone close, taking a B707-321C into Lasham.
As to engine-out field lengths (if any) --- any idea where they (or any "data" for other non-normal approach conditions) might come from??
As to what is manufacturer's "certified" data in an aeroplane performance manual -- that is a whole other can of worms, where those who have never bothered to acquaint them selves with the facts argue their misconceptions.
Tootle pip!!
