Engine out / Decompression ETP's/CP's
I am probably missing something but can someone explain the point of determining separate ETP's for the engine failure or decompression/emergency descent cases?
I thought that as the failure is assumed to occur at the normal ( ie. everything working as advertised) ETP then there would be no difference in the time taken to continue or return at the reduced speed corrected for the wind . I guess what I mean is will or how will the ETP's differ for the above scenarios? Any help greatly appreciated. |
Different fuel flows/True Airspeeds/Ground speeds for the two cases.
Chuck. |
jalbert
Consider the following scenario. Norm Ops - TAS 400, HWC 50 kts Asy Ops - TAS 330, HWC 50 kts Sector - 1000 nm. Therefore: NGSO - 350 kts NGSH - 450 kts AGSO - 280 kts AGSH - 380 kts Normal Ops CP > 1000/800 [TAS x2 or GSO + GSH] = a factor of 1.25. Asy Ops CP > 1000/660 [TAS x2 or GSO + GSH] = a factor of 1.515
Now just plug in the the appropriate values and you will find that:
However:
So if blogs the pax has a heart attack and thus a quick landing is required, at normal ops anything further from Home than 562.5 nm means it is quicker to continue than return. However should bloggs have his heart attack whilst Asymmetric, the CP moves to 575.8 nm of Home, some 13 nm further along track. This example doesn't consider the possibility of having to chose a lower level due Asy situation. Stronger winds or a greater diff between Norm & Asy ops will cause the CP to move more. (ETE @ Norm CP = 96.4 mins. ETE @ Asy CP = 98.7 mins) [ 07 August 2001: Message edited by: Capt Claret ] |
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