More Cat "A"
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Steve 76,
"I am still not convinced that 'CDP' is not specifically a Catagory A term."
I guess if we get into the nitty gritty we can argue the use of CDP for CAT A only proceedures till the proverbial cows come home.
The only point that I really want to make in response, is the fact that the terminology of 'CDP' perfectly describes the situation that you are faced with if and when an engine fails in a twin. The pilot does not have a 'descision' about what he will do prior to CDP. This is not interpretation, it is fact, you can not continue with the take off as the aircraft does not have the ability to stay level let alone climb OEI. It is why the pilot must be aware of the 'critical descision point' with regard to ambient conditions prior to take off no matter if he is operating to CAT A or not.
Once CDP is reached then the pilot starts to earn the money he is paid for driving a twin. He must now make a 'descision' whether to reject the take off or continue with the flight. Once again, this is the same whether you are operating to CAT A, CAT B or any other profile you want to follow.
Sorry to harp on about it, but I cannot think of any other way of describing the point where I have to make that kind of descision.....
Anyone?
P.S - Steve, I like your use of the word 'dummy', very polite for a Kiwi
"I am still not convinced that 'CDP' is not specifically a Catagory A term."
I guess if we get into the nitty gritty we can argue the use of CDP for CAT A only proceedures till the proverbial cows come home.
The only point that I really want to make in response, is the fact that the terminology of 'CDP' perfectly describes the situation that you are faced with if and when an engine fails in a twin. The pilot does not have a 'descision' about what he will do prior to CDP. This is not interpretation, it is fact, you can not continue with the take off as the aircraft does not have the ability to stay level let alone climb OEI. It is why the pilot must be aware of the 'critical descision point' with regard to ambient conditions prior to take off no matter if he is operating to CAT A or not.
Once CDP is reached then the pilot starts to earn the money he is paid for driving a twin. He must now make a 'descision' whether to reject the take off or continue with the flight. Once again, this is the same whether you are operating to CAT A, CAT B or any other profile you want to follow.
Sorry to harp on about it, but I cannot think of any other way of describing the point where I have to make that kind of descision.....
Anyone?
P.S - Steve, I like your use of the word 'dummy', very polite for a Kiwi
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Xnr
Nick
I have a question about the Cat A reject (failure prior to CDP)
When you reject, did you flare off as much airspeed as you could and pull the snot out of the remaining engine using decaying Nr to cushion your landing? (in an effort to keep the procedure reject distances as short as possible)
OR
Did you lower the pole maintaining the nose up atitude (10 degrees max when less than 30') allow the aircraft to touch and apply the brakes, using 2.5 min OEI pwr only?
Cheers
I have a question about the Cat A reject (failure prior to CDP)
When you reject, did you flare off as much airspeed as you could and pull the snot out of the remaining engine using decaying Nr to cushion your landing? (in an effort to keep the procedure reject distances as short as possible)
OR
Did you lower the pole maintaining the nose up atitude (10 degrees max when less than 30') allow the aircraft to touch and apply the brakes, using 2.5 min OEI pwr only?
Cheers
Last edited by Xnr; 31st Aug 2002 at 03:40.
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On the A+ we use 65 knots as our Vtoss for group/cat A. We use 52 knots for our group B initial climb to clear obstacles, although it has been suggested that we might as well accellerate to 65 and acchieve Vtoss with a minimum of effort.
Does anyone else apart from us on the North Sea use these numbers that way?
Does anyone else apart from us on the North Sea use these numbers that way?
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CDP is a Cat A term, it is specifically where one must make the critical decision, go or stay. Go occurs after CDP, stay is before or at.
Regarding Xnr's question of how to reject, I suggest the method that harms the aircraft least. If your takeoff area is exactly the Rejected Takeoff distance, so that the large Oak Tree has your name on it if you do not flare agressively and then pull the snot out of the engine, by all means do so. In fact, I assure you that you will, since Oak is tougher than air, and you instinctively know that!
When we set the distance in test to produce the RFM charts, we use still air, max weight and an engine that is set to produce only the 2.5 min power. It does not over temp and over torque, so we have eliminated that nice source of extra power. In the real case, you have that available to you, and it helps make the distance shorter.
By all means don't pull the OEI ratings in routine practice, as you will reduce engine life. I almost always simply practice using two motors, and half the single torque in dual engine mode. This allows lots of escapes, little engine wear, and no danger of an all-thumbs person cutting both of those noisey suckers, thus creating that awesome silence that some only dream about.
The Vtoss for US and UK procedures is somewhat different, as I recall, since the old BCAR climb gradient is steeper than the FAA climb (BCAR was gven as a percent gradient, I believe 100 feet per mile, FAA was a simple 100 feet per minute climb rate), so we had to get closer to Vy to allow the better climb in the UK manual.
Regarding Xnr's question of how to reject, I suggest the method that harms the aircraft least. If your takeoff area is exactly the Rejected Takeoff distance, so that the large Oak Tree has your name on it if you do not flare agressively and then pull the snot out of the engine, by all means do so. In fact, I assure you that you will, since Oak is tougher than air, and you instinctively know that!
When we set the distance in test to produce the RFM charts, we use still air, max weight and an engine that is set to produce only the 2.5 min power. It does not over temp and over torque, so we have eliminated that nice source of extra power. In the real case, you have that available to you, and it helps make the distance shorter.
By all means don't pull the OEI ratings in routine practice, as you will reduce engine life. I almost always simply practice using two motors, and half the single torque in dual engine mode. This allows lots of escapes, little engine wear, and no danger of an all-thumbs person cutting both of those noisey suckers, thus creating that awesome silence that some only dream about.
The Vtoss for US and UK procedures is somewhat different, as I recall, since the old BCAR climb gradient is steeper than the FAA climb (BCAR was gven as a percent gradient, I believe 100 feet per mile, FAA was a simple 100 feet per minute climb rate), so we had to get closer to Vy to allow the better climb in the UK manual.
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Thanx Nick
No we are not training like that just wondering how the profile was flown for certification.
There are some who believe that the reject should be flown so that the aircraft is pretty much stopped as it touches down. That would leave you no choice but to use transient pwr. ( we artificially top our engines so that they cant be overtemped or overtorqued) thus the decaying rotor.
a little riskier than limited twin engine pwr I know.
I say that the aircraft should touch down as slow as it can without exceeding any engine limits (in our case decaying rotor)and apply the brakes. You will be well within the rejected Cat A distances.
Cheers
No we are not training like that just wondering how the profile was flown for certification.
There are some who believe that the reject should be flown so that the aircraft is pretty much stopped as it touches down. That would leave you no choice but to use transient pwr. ( we artificially top our engines so that they cant be overtemped or overtorqued) thus the decaying rotor.
a little riskier than limited twin engine pwr I know.
I say that the aircraft should touch down as slow as it can without exceeding any engine limits (in our case decaying rotor)and apply the brakes. You will be well within the rejected Cat A distances.
Cheers
Last edited by Xnr; 31st Aug 2002 at 05:34.
Xnr,
I dont agree. If I have a donk failure, I am going to pull as much as I need out of the remaining one in order to achieve a safe rate of descent at touch down. If my need is greater than the TQ limit, Temp limit, or N1/NG - then I win and the engine gets torched!! I will pull to the bleed.
This reminds me of a mate who pulled out of a wing over just a tad too low and ripped the skids of a Jet Ranger. He exclaimed: "at least I didnt over torque it". IMHO, stuff the engine, I am trying to save my arse.
I have to agree with rotorque re the CDP. I use it during all twin take offs, very few of which I have Cat A performance, and I even use it for limited power single engine helo work when deciding to go or abort. Besides, you Cat A guys cant have all the groovy words.
I dont agree. If I have a donk failure, I am going to pull as much as I need out of the remaining one in order to achieve a safe rate of descent at touch down. If my need is greater than the TQ limit, Temp limit, or N1/NG - then I win and the engine gets torched!! I will pull to the bleed.
This reminds me of a mate who pulled out of a wing over just a tad too low and ripped the skids of a Jet Ranger. He exclaimed: "at least I didnt over torque it". IMHO, stuff the engine, I am trying to save my arse.
I have to agree with rotorque re the CDP. I use it during all twin take offs, very few of which I have Cat A performance, and I even use it for limited power single engine helo work when deciding to go or abort. Besides, you Cat A guys cant have all the groovy words.
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Helmet Fire
Don't get me wrong if you need it ....use it ....we are talking about training here and how the procedure was flown for certification.
Don't spare the engine and write off the aircraft.
Thats why the Cat A profile was designed. The aircraft is supposed to be able to safely reject prior to CDP or safely fly away after CDP.
If you have to abuse the machine to do that, then you haven't calculated something right. (gross weight, distance, density altitude for instance)
Cheers
Don't get me wrong if you need it ....use it ....we are talking about training here and how the procedure was flown for certification.
Don't spare the engine and write off the aircraft.
Thats why the Cat A profile was designed. The aircraft is supposed to be able to safely reject prior to CDP or safely fly away after CDP.
If you have to abuse the machine to do that, then you haven't calculated something right. (gross weight, distance, density altitude for instance)
Cheers
Last edited by Xnr; 31st Aug 2002 at 07:00.
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CDP?
§__29.55 _Takeoff decision point (TDP): Category A.
(a) The TDP is the first point from which a continued takeoff capability is assured under §__29.59 and is the last point in the takeoff path from which a rejected takeoff is assured within the distance determined under §29.62.
(b) The TDP must be established in relation to the takeoff path using no more than two parameters; e.g., airspeed and height, to designate the TDP.
(c) Determination of the TDP must include the pilot recognition time interval following failure of the critical engine.
§__29.77 _Landing Decision Point (LDP): Category A.
(a) The LDP is the last point in the approach and landing path from which a balked landing can be accomplished in accordance with §__29.85.
(b) Determination of the LDP must include the pilot recognition time interval following failure of the critical engine.
What is CDP?
§__29.55 _Takeoff decision point (TDP): Category A.
(a) The TDP is the first point from which a continued takeoff capability is assured under §__29.59 and is the last point in the takeoff path from which a rejected takeoff is assured within the distance determined under §29.62.
(b) The TDP must be established in relation to the takeoff path using no more than two parameters; e.g., airspeed and height, to designate the TDP.
(c) Determination of the TDP must include the pilot recognition time interval following failure of the critical engine.
§__29.77 _Landing Decision Point (LDP): Category A.
(a) The LDP is the last point in the approach and landing path from which a balked landing can be accomplished in accordance with §__29.85.
(b) Determination of the LDP must include the pilot recognition time interval following failure of the critical engine.
What is CDP?
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CDP - Critical Decision Point
The difference is that in the Cat A profile CDP(S76A) is clearly defined (35 knots / 40' ) and comes with the Sikorsky (Nick Lappos) guarantee of success if flown correctly and the WAT chart for the profile is observed. (without exceeding any limits or use of transients, I might add)
The B profile has a variable DECISION POINT dependent on weight ,wind ,OAT, and obstacles etc. It comes with no guarantee from Sikorsky. The decision is all yours. You make the big bucks. But.......you better get it right....... for it is every bit as CRITICAL.
Cheers
The difference is that in the Cat A profile CDP(S76A) is clearly defined (35 knots / 40' ) and comes with the Sikorsky (Nick Lappos) guarantee of success if flown correctly and the WAT chart for the profile is observed. (without exceeding any limits or use of transients, I might add)
The B profile has a variable DECISION POINT dependent on weight ,wind ,OAT, and obstacles etc. It comes with no guarantee from Sikorsky. The decision is all yours. You make the big bucks. But.......you better get it right....... for it is every bit as CRITICAL.
Cheers
Last edited by Xnr; 31st Aug 2002 at 17:23.
Thread Starter
Thanks fellow pilots,
Its abnormally pedantic of me to argue over terminology, but the point here is that CDP defines a profile as Cat A and thus identifies to the pilot that he has options during the proceedure.
I think in our operation that this needs to be identified and corrected for the benefit of the aircrew.
Safe Flying
Its abnormally pedantic of me to argue over terminology, but the point here is that CDP defines a profile as Cat A and thus identifies to the pilot that he has options during the proceedure.
I think in our operation that this needs to be identified and corrected for the benefit of the aircrew.
Safe Flying
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Oh, John Bicker, you are a very persnikity person, amplified by the fact that you are correct. I hate when that happens! Current usage carefully separates TDP from LDP, older usage used the ambiguous CDP. I am guilty of being in the older classification, I guess.
1964 FAR:
Sec. 29.53
Takeoff: Category A.
(a) General. The takeoff performance must be determined and scheduled so that, if one engine fails at any time after the start of takeoff, the rotorcraft can--
(1) Return to, and stop safely on, the takeoff area; or
(2) Continue the takeoff and climbout, and attain a configuration and airspeed allowing compliance with Sec. 29.67(a)(2).
(b) Critical decision point. The critical decision point must be a combination of height and speed selected by the applicant in establishing the flight paths under Sec. 29.59. The critical decision point must be obtained so as to avoid the critical areas of the limiting height-speed envelope established under Sec. 29.79.
1964 FAR:
Sec. 29.53
Takeoff: Category A.
(a) General. The takeoff performance must be determined and scheduled so that, if one engine fails at any time after the start of takeoff, the rotorcraft can--
(1) Return to, and stop safely on, the takeoff area; or
(2) Continue the takeoff and climbout, and attain a configuration and airspeed allowing compliance with Sec. 29.67(a)(2).
(b) Critical decision point. The critical decision point must be a combination of height and speed selected by the applicant in establishing the flight paths under Sec. 29.59. The critical decision point must be obtained so as to avoid the critical areas of the limiting height-speed envelope established under Sec. 29.79.
