Speed flown after Drifting down?
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my bad @73qanda i meant VMRC...and what u said makes sense given it is a "smoke" event...but like i said not withstanding peculiarities of specific contingencies which can be many requiring different courses of action...am only talking about a simple engine failure event with no other problems accompanying.
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i'll try to breakit down...
1. Why the speed to be flown after engine failure and subsequent drift down is LRC(several checklists mention that) and not MRC since range is the worst affected flight parameter?
2. Does time has any significance in this(as we know LRC is a faster than MRC and would take a lil less time), since ETOPS also imposes time limits at OEI cruise speed? If so how does it play its part?
2. Does time has any significance in this(as we know LRC is a faster than MRC and would take a lil less time), since ETOPS also imposes time limits at OEI cruise speed? If so how does it play its part?
1/ It is a nice balance between fuel efficiency and time spent aloft single engine.
( ie 1% more fuel but 5% less time)
2/ Time is a factor as per the statement above.
The role that time plays for OEI cruise is mainly at the planning stage. Your company would have had approval for a maximum time and then used a relatively fast speed in order to get a descent range ring of operations, that doesn't mean you have to fly that speed. The speed you do fly is up to the crew at the time ( Captain ultimately). Some companies place a maximum to aid in decsion making airborne.
For example, if you are unlucky enough to have a failure at the most critical point and then flew the speed that the company based it's EDTO application on you would arrive at your chosen field with much less fuel than if you flew s/e LRC.
Each situation will be different. If you have a lot of fuel you might want to go faster to minimise the time aloft. If fuel is critical you might accept being airborn a bit longer in order to arrive with more fuel.
Does that help?
( ie 1% more fuel but 5% less time)
2/ Time is a factor as per the statement above.
, since ETOPS also imposes time limits at OEI cruise speed? If so how does it play its part?
For example, if you are unlucky enough to have a failure at the most critical point and then flew the speed that the company based it's EDTO application on you would arrive at your chosen field with much less fuel than if you flew s/e LRC.
Each situation will be different. If you have a lot of fuel you might want to go faster to minimise the time aloft. If fuel is critical you might accept being airborn a bit longer in order to arrive with more fuel.
Does that help?
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What speed to fly is like asking how long a piece of string is? Assuming you are in a twin engine aircraft. Many factors come into play,
If you have a short distance to go do you want to be flying at LRC then having to hold because you still haven't completed all of your approach preparations.
As for ETOPS, your company through the regulatory authority will have approved you to a certain time limit, using this time limit a maximum diversion distance will be calculated (under EASA, isa, nil wind etc etc). Assuming the worst happens and an engine failure occurs at the ETP (which coincides to be at the maximum diversion distance) you may exceed (legally) your ETOPS time limit due to actual winds, not flying the diversion speed as defined in your operations manual etc.
If you have a short distance to go do you want to be flying at LRC then having to hold because you still haven't completed all of your approach preparations.
As for ETOPS, your company through the regulatory authority will have approved you to a certain time limit, using this time limit a maximum diversion distance will be calculated (under EASA, isa, nil wind etc etc). Assuming the worst happens and an engine failure occurs at the ETP (which coincides to be at the maximum diversion distance) you may exceed (legally) your ETOPS time limit due to actual winds, not flying the diversion speed as defined in your operations manual etc.
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always helpful @framer.....bt some irritating doubts still linger....is LRC chosen jst b'cuz it feels like a "nice speed"?or does it have some solid reason cuz like i said range wud be worst affected in oei thus somehow making MRC sound a better speed to me...we can thence always adjust our speed according to the requirements of a particular scenerio for eg LRC or even a higher speed etc..
