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DP's, climb gradient, 2nd segment
- Thread starter soarby007
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Lead Sled
Sitt'n on the throne...
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Has anyone ever seen an "all-engines operational" climb chart for any of the multi-engine turbo-jet aircraft we're flying? I you have, let me know - the manufacturers are required to give you that data and they don't. So how do we know that we can even do it under normal conditions? Soarby007 it's going to take time for this "new" concept to drift down to the various instructors. I've sat in on some performance classes where the instructors were pretty incredulous. Early on, I found it best just to sit back and smile. Fortunately, it's changing and I agree with HMR, the AC is pretty clear and you did what I would have done - forwarded the reference so that he can look it up and read it for himself.
LS
My 2 cents...
The numbers in DPs are what it takes to clear the obstacles. The DP's minimum gradients don't care if you use 1, 2, or 5 engines.
Where this whole single engine stuff comes into play is in the aircraft's performance section. Those numbers are based on your aircraft's single engine climb performance, which is what the Feds expect you to use when flying a DP.
Hope this helps!
Actually I disagree with this. The "Feds" just published the AC 120-91 emphasizing that DP's are not single engine procedures and never designed to be.
Not all DP's are obstacle procedures. However, on some DP's I may not want to continue to climb on one engine just to complete the procedure. LAS is a good example on the Cowby2. Why would I continue toward the mountains on one engine. That's why you need an escape procedure in an emergency. I wouldn't want to complete a normal DP procedure, in all cases(in an emergency), simply to say that I complied with the regulations.
The performance numbers in most business aircraft are good to 1500', that's it. In the Westwind, there is not one shred of data to indicate what airspeed, climb rate, etc is to be accomplished after 1500', on one engine to meet any gradient. There happens to be a two engine rate of climb chart, but not a single engine climb chart. Also, this AC 120-91 points out that a number of things will degrade your climb gradient, i.e. angle of bank, temperature, etc., all the things we all know. None of this is in the manufacturer's data.
I agree that APG has good information for an escape procedure, not necessarily designed to a DP, but to get you somewhere safely.
Like I told the instructor, you still have to have a plan after 1500'. What will it be? And how will you accomplish it thru proven data not guesswork, such as a V2 plus something. You can't take off knowing that the DP's are all engine procedures, clutching your lucky rabbit foot in hopes nothing will happen. My TFE731 failed at 20,000' last year, could have been at 400' or 8,000'.
Gotta have a plan.
The numbers in DPs are what it takes to clear the obstacles. The DP's minimum gradients don't care if you use 1, 2, or 5 engines.
Where this whole single engine stuff comes into play is in the aircraft's performance section. Those numbers are based on your aircraft's single engine climb performance, which is what the Feds expect you to use when flying a DP.
Hope this helps!
Actually I disagree with this. The "Feds" just published the AC 120-91 emphasizing that DP's are not single engine procedures and never designed to be.
Not all DP's are obstacle procedures. However, on some DP's I may not want to continue to climb on one engine just to complete the procedure. LAS is a good example on the Cowby2. Why would I continue toward the mountains on one engine. That's why you need an escape procedure in an emergency. I wouldn't want to complete a normal DP procedure, in all cases(in an emergency), simply to say that I complied with the regulations.
The performance numbers in most business aircraft are good to 1500', that's it. In the Westwind, there is not one shred of data to indicate what airspeed, climb rate, etc is to be accomplished after 1500', on one engine to meet any gradient. There happens to be a two engine rate of climb chart, but not a single engine climb chart. Also, this AC 120-91 points out that a number of things will degrade your climb gradient, i.e. angle of bank, temperature, etc., all the things we all know. None of this is in the manufacturer's data.
I agree that APG has good information for an escape procedure, not necessarily designed to a DP, but to get you somewhere safely.
Like I told the instructor, you still have to have a plan after 1500'. What will it be? And how will you accomplish it thru proven data not guesswork, such as a V2 plus something. You can't take off knowing that the DP's are all engine procedures, clutching your lucky rabbit foot in hopes nothing will happen. My TFE731 failed at 20,000' last year, could have been at 400' or 8,000'.
Gotta have a plan.
The AC does not negate the requirement to avoid obstacles with an engine inoperative and to read it that way falls short. The AC simply describes the basics for the design of departures for third parties. It does however describe the underlying requirements.
From AC 120-91
10. METHODS OF ANALYSIS. Sections 121.189, 135.379, and 135.398 require that the net takeoff flightpath clears all obstacles by either 35 feet vertically or 200 feet laterally inside the airport boundary, or 300 feet laterally outside the airport boundary.
The one engine inoperative requirement is harder to find but is present in the CFRs quoted in the AC. The first one for example, 121.189 states (among other things):
2) In the case of an airplane certificated after September 30, 1958 (SR 422A, 422B), that allows a net takeoff flight path that clears all obstacles either by a height of at least 35 feet vertically, or by at least 200 feet horizontally within the airport boundaries and by at least 300 feet horizontally after passing the boundaries.
and it goes on to say:
g) For the purposes of this section the terms, takeoff distance, takeoff run, net takeoff flight path and takeoff path have the same meanings as set forth in the rules under which the airplane was certificated.
Part 25 contains those rules and defines Takeoff Path as (again among other things):
(2) The airplane must be accelerated on the ground to VEF, at which point the critical engine must be made inoperative and remain inoperative for the rest of the takeoff;
The other CFRs quoted have similar language.
Just beacuse the AC states SIDs assume all engines operating doesn't alleviate the basics. If there is a reverse print "T" on the plate then there is an Obstacle Departure Procedure (ODP) for that airport and you should look it up in the front and comply with it one engine inoperative for commercial operations. If there's none then a minimum of 200 FT/Nm is required, 3.3%, again one engine inoperative. The AC itself states in the begining:
This AC need not serve as the sole basis for determining whether an obstacle analysis program meets the intent of the regulations.
Why we use one engine inoperatve versus say the gear remaining down? Arbitrary. Ironically I've had the gear stay down on me three times but have never lost an engine below 1000'. But that's the way it is.
From AC 120-91
10. METHODS OF ANALYSIS. Sections 121.189, 135.379, and 135.398 require that the net takeoff flightpath clears all obstacles by either 35 feet vertically or 200 feet laterally inside the airport boundary, or 300 feet laterally outside the airport boundary.
The one engine inoperative requirement is harder to find but is present in the CFRs quoted in the AC. The first one for example, 121.189 states (among other things):
2) In the case of an airplane certificated after September 30, 1958 (SR 422A, 422B), that allows a net takeoff flight path that clears all obstacles either by a height of at least 35 feet vertically, or by at least 200 feet horizontally within the airport boundaries and by at least 300 feet horizontally after passing the boundaries.
and it goes on to say:
g) For the purposes of this section the terms, takeoff distance, takeoff run, net takeoff flight path and takeoff path have the same meanings as set forth in the rules under which the airplane was certificated.
Part 25 contains those rules and defines Takeoff Path as (again among other things):
(2) The airplane must be accelerated on the ground to VEF, at which point the critical engine must be made inoperative and remain inoperative for the rest of the takeoff;
The other CFRs quoted have similar language.
Just beacuse the AC states SIDs assume all engines operating doesn't alleviate the basics. If there is a reverse print "T" on the plate then there is an Obstacle Departure Procedure (ODP) for that airport and you should look it up in the front and comply with it one engine inoperative for commercial operations. If there's none then a minimum of 200 FT/Nm is required, 3.3%, again one engine inoperative. The AC itself states in the begining:
This AC need not serve as the sole basis for determining whether an obstacle analysis program meets the intent of the regulations.
Why we use one engine inoperatve versus say the gear remaining down? Arbitrary. Ironically I've had the gear stay down on me three times but have never lost an engine below 1000'. But that's the way it is.
G100driver
Well-known member
- Joined
- Jun 18, 2002
- Posts
- 2,094
3/4 of the guys out here in the corporate world have no idea what you are talking about. Alternate Departure Procdures are just starting to take hold, but FSI is still way behind the power curve in teaching these.
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