Engine out terrain clearance
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Originally Posted by JammedStab
Runway track is what is done for most runways after an engine failure at my company. Heading Select and compensate for wind.
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Just to make sure I'm on the right line
Let’s say you had a climbing CAS of 90kts with a 15kt headwind, where your pressure height is 4,000’ and temperature is 12C, how many feet per minute (FPM) do you have to achieve to ensure obstacle clearance using 6% gradient?
Using a flight computer, enter PH 4,000, Temp 12 and CAS 90.
TAS = 86kts
Now deduct the headwind:
86 - 15 = 71kts ground speed (GS)
Using the rule of thumb GS / FPM = Climb gradient (in %)
6 x 71 = 426FPM
To check the answer is correct (assuming slight error in rule of thumb), let’s work it the long way.
71kts = 71 x 6076 (feet in NM) / 60 (minutes is hour) = 7190 FPM (horizontally)
7190 x 0.06 (gradient) = 431FPM
Copy copy?
Let’s say you had a climbing CAS of 90kts with a 15kt headwind, where your pressure height is 4,000’ and temperature is 12C, how many feet per minute (FPM) do you have to achieve to ensure obstacle clearance using 6% gradient?
Using a flight computer, enter PH 4,000, Temp 12 and CAS 90.
TAS = 86kts
Now deduct the headwind:
86 - 15 = 71kts ground speed (GS)
Using the rule of thumb GS / FPM = Climb gradient (in %)
6 x 71 = 426FPM
To check the answer is correct (assuming slight error in rule of thumb), let’s work it the long way.
71kts = 71 x 6076 (feet in NM) / 60 (minutes is hour) = 7190 FPM (horizontally)
7190 x 0.06 (gradient) = 431FPM
Copy copy?
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In regards to a takeoff, it seems most places, the engine out procedure is to fly runway heading(track) as the engineers have analyzed the surrounding terrain for obstacle clearance. But how far out are they required to analyze.
If someone decided to take a really long time with all their procedures and continue straight out, they could go quite far. There are some locations with distant mountains as we all know.
If someone decided to take a really long time with all their procedures and continue straight out, they could go quite far. There are some locations with distant mountains as we all know.
What criteria is used to provide obstruction clearance during departure?
The 40:1 obstacle identification surface (OIS) begins at the departure end of runway (DER) and slopes upward at 152 FPNM until reaching the minimum IFR altitude or entering the en route structure. This assessment area is limited to 25 NM from the airport in non-mountainous areas and 46 NM in designated mountainous areas. Beyond this distance, the pilot is responsible for obstacle clearance if not operating on a published route, if below (having not reached) the MEA or MOCA of a published route, or an ATC assigned altitude.
http://tfmlearning.fly.faa.gov/publi...5/aim0502.html
I wonder what it is for engine out procedures?
Most charted perf data ends at 30nm. Here’s the FAA AC, but it doesn’t specify a limiting distance.
https://www.faa.gov/documentLibrary/...r/AC120-91.pdf
https://www.faa.gov/documentLibrary/...r/AC120-91.pdf
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Here is a document with page highlighted explaining how far there is an analysis for terrain after which point, there could be a tall mountain...like Calgary or Denver don't go straight out forever. Look at Fig. 5-2-1
https://books.google.ca/books?id=x8j...0miles&f=false
or google faa ocs 25/46 miles to get to the exact page on the appropriate link provided.
(Note: The AIM can be linked somewhat more easily at https://www.faa.gov/air_traffic/publ.../media/aim.pdf The book reference is at page 5.2.7 - JT)
https://books.google.ca/books?id=x8j...0miles&f=false
or google faa ocs 25/46 miles to get to the exact page on the appropriate link provided.
(Note: The AIM can be linked somewhat more easily at https://www.faa.gov/air_traffic/publ.../media/aim.pdf The book reference is at page 5.2.7 - JT)
Just read Post No. 8
Surely you are not serious
Presumably you have never had the pleasure of a real engine failure at or after V1 on an obstacle limited/second segment climb limited weight weight at night or IMC where the obstacles are there but you cannot see and avoid. You and your passengers are then totally reliant on some Performance Engineer knowing his job such that you will clear terrain/obstacles by the regulatory margin only if you fly the profile exactly as per the runway analysis instructions.
25 years of trouble free operations means SFA. It means you have just had good fortune where your doubtless superior airmanship was not needed
We are paid to take care of things and given a manual to assist us but not handicap us.
25 yrs of doing this with no violations, write ups by anybody and no scraped metal worked for me
25 yrs of doing this with no violations, write ups by anybody and no scraped metal worked for me
Presumably you have never had the pleasure of a real engine failure at or after V1 on an obstacle limited/second segment climb limited weight weight at night or IMC where the obstacles are there but you cannot see and avoid. You and your passengers are then totally reliant on some Performance Engineer knowing his job such that you will clear terrain/obstacles by the regulatory margin only if you fly the profile exactly as per the runway analysis instructions.25 years of trouble free operations means SFA. It means you have just had good fortune where your doubtless superior airmanship was not needed
Last edited by Judd; 7th Jan 2018 at 00:54.
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Here is a document with page highlighted explaining how far there is an analysis for terrain after which point, there could be a tall mountain...like Calgary or Denver don't go straight out forever.
or google faa ocs 25/46 miles to get to the exact page on the appropriate link provided.
or google faa ocs 25/46 miles to get to the exact page on the appropriate link provided.
The assumption: with all engines operating you will be level at a legal IFR altitude within those distances.
With OEI it becomes the operator's responsibility to assess the takeoff and en route-climb flight path. At a places such as Calgary or Denver the operator's performance department needs to design OEI routes that don't go straight-out into high terrain..
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at what distance should they become concerned and make a turn?
Depends on the rocky bits and pieces.
Can't reasonably be done on the fly (unless the local terrain be quite benign) but, rather, needs to be done back in the office.
Hence the usual deal that the operator gets the work done and schedules any requirements for crew use.
Depends on the rocky bits and pieces.
Can't reasonably be done on the fly (unless the local terrain be quite benign) but, rather, needs to be done back in the office.
Hence the usual deal that the operator gets the work done and schedules any requirements for crew use.
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This is entirely correct...
There is NO criteria for EO. NONE. Procedures that have an OEI track, rely on the engineering dept to load the ac accordingly.
The ONLY answer is that is varies very specifically by aircraft. Performance in a turn OEI is usually far less that anyone anticipates, especially when it is warm.
U.S. TERPS is only for all engines operating. In non-mountainous areas the IFR obstacle departure procedure (ODP) is assessed out to 25 miles. In regulatory Designated Mountainous Areas (DMAs) the assessment is to 46 miles. If a 40:1 performance surface cannot be maintained in all directions, then a route ODP must be developed for publication.
The assumption: with all engines operating you will be level at a legal IFR altitude within those distances.
With OEI it becomes the operator's responsibility to assess the takeoff and en route-climb flight path. At a places such as Calgary or Denver the operator's performance department needs to design OEI routes that don't go straight-out into high terrain..
The assumption: with all engines operating you will be level at a legal IFR altitude within those distances.
With OEI it becomes the operator's responsibility to assess the takeoff and en route-climb flight path. At a places such as Calgary or Denver the operator's performance department needs to design OEI routes that don't go straight-out into high terrain..
The ONLY answer is that is varies very specifically by aircraft. Performance in a turn OEI is usually far less that anyone anticipates, especially when it is warm.
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There is NO criteria for EO. NONE.
Not absolutely correct. The normal take off weight limits cover WAT requirements for climb OEI.
However, when it comes to terrain clearance, you are correct .. it's up to the operator/pilot to make sure that the data has been acquired and the sums done to establish a suitable maximum weight for the day to ensure that, at the very least, the minimum terrain clearances for the net flight path are met.
The ONLY answer is that is varies very specifically by aircraft.
To some extent, the numbers will have some similarity for twins, triples, and quads as the WAT requirements vary with the number of engines.
Not absolutely correct. The normal take off weight limits cover WAT requirements for climb OEI.
However, when it comes to terrain clearance, you are correct .. it's up to the operator/pilot to make sure that the data has been acquired and the sums done to establish a suitable maximum weight for the day to ensure that, at the very least, the minimum terrain clearances for the net flight path are met.
The ONLY answer is that is varies very specifically by aircraft.
To some extent, the numbers will have some similarity for twins, triples, and quads as the WAT requirements vary with the number of engines.
Here’s what the FAA puts out:
https://www.faa.gov/documentLibrary/...r/AC120-91.pdf
Under fire. Not entirely true, this AC referenced above is not regulatory ( I believe) but is the guidance used by most operators or perf engineers.
https://www.faa.gov/documentLibrary/...r/AC120-91.pdf
Under fire. Not entirely true, this AC referenced above is not regulatory ( I believe) but is the guidance used by most operators or perf engineers.
