More Cat "A"

[Steve76]

:rolleyes:
Yet more 76 chat.....

Quicky for all twin drivers.

Scenario: Cat A takeoff. Light weight, thus oddles of power.
Problem: Chart shows that you should apply takeoff power and 5 degrees nosedown.

Therefore; If you apply Max T/O pwr the required attitude may be 15 degrees nose down. To maintain the 5 degrees the only option is to reduce power and that, to my mind, extends the distance required for the proceedure.

Let the games begin and thanks in advance for your thoughts.

Steve :cool:

[Hingeless Rotor]

Hi Steve,

I think the 5 degrees is a figure used to stop pilots from nosing over too far at the initial hover to transition part of the take off. Nosing over too far reduces your ability to get it back up again if you have to abort the takeoff prior to CDP.



"I thought I was wrong once....... but I was mistaken"

[SASless]

If very light....the question is more like "Who is looking?". If the thing will hover on one engine....are you really concerned about "Cat A " performance? Also, generally, the profiles have a limitation clause....something along the line of hover power plus a fixed percentage of power not to exceed maximum power or not to exceed that artificial limit of power. That allows you to fly the prescribed Cat A profile irregardless of excess power available.

[S76Heavy]

I feel that at light weights a 10% Tq margin over hover tq seems to do the trick nicely. It helps when one flies from virtually the same runway everey time, though.
IMO there is little difference in a max AUM cat a and a lighter one as described above.
As long as you can abort within the distance available, why pull all the power and make the pax's life miserable?

[donut king]

One thing to remember is that the flight manual procedure(s) are advisory/ reference.

The limitations section are mandatory while other proc's are reference.

I agree, max power= >5 degrees nose down. Therefore I use what is req'd only. 15 degrees nose down( to exaggerate) followed by an engine failure.... that nose is going for the runway, as you know.

[Helinut]

It is an interesting question, especially for those types where the profile/procedures says "use max two engine take-off power".

I may well be wrong, but where the helicopter is very light and it is not a tight site I ease up on the power a bit.

I wonder whether certification for newer types has taken this into account. For example, for the EC 135 you are supposed to pull IGE hover power + 10%.

[Nick Lappos]

Steve,

That is a glitch in the procedures, and was created by yours truly. When light, it is actually quite alright to just use 10% increase in torque over hover power, since that is about the excess power you have under the conditions that the Cat A procedure was developed (10,300 pounds, hot day).

It works.

Nick

[offshoreigor]

Hi Steve!

The principle of Cat A on the 76, is to stay at the 5-10' wheel height 35 KIAS on an A/A+ model and V2 (approx 55 KIAS) on an A++. If you allow the aircraft to climb higher, then fly away, land back is not guaranteed. On the A++, we use hover Q plus 6% and adjust as required to maintain the 5-10' until V2. In our operation assuming a standard 32C at MSL and at least a 2400' takeoff area our CDP is 45KIAS and our V2 is 55KIAS. Keep in mind that with the A++ there are three OEI scenarios instead of two with the A and A+. First we have OEI prior to 35 KIAS, OEI between 35 and 45 KIAS and OEI after CDP. Each scenario depends on the 5-10' wheel height.

In summary, although the procedure is well layed out on the A++, there is nothing wrong with applying the same procedure to the A and A+, that is to say, hover Q plus a margin that will maintain the 5-10' wheel height until rotation.

Hope that helps!

Cheers :eek: OffshoreIgor :eek:

PS Craig says Hi.

[S76Heavy]

Just out of curiosity, what exactly is the OEI scenario between 35 and 45 KIAS?

[Steve76]

Thanks to ALL for your input...

The last operation I flew the 76 in used the hover +10% method.

No problems.

Here we have no set figure and is is always a discussion point when one of my trainees goes for a checkride and applies "Takeoff power" and the subsequent 15 degrees nose down. Our op's manual calls for 5 degrees nose down as a limit so it always raises the eyebrows.

Some guys have all been briefed to pull to max takeoff power (100% if available) by other training pilots.

Typically during the recurrent training I do with them, I limit the power to a TQ of 75% (eg..) to simulate a heavier power limited aircraft, so the excess power thing is not a factor. However, during the ride there is no limit imposed, so the guys pull until they reach the first engine limit.

Yesterday, I got into the Flight Safety manual after looking in Ops and aircraft books and looked for a definition of "takeoff power".
The flight safety manual refers to a chart in the performance(?) section which calcuates your max TQ for a Cat A departure based on the OAT, PA etc etc...

Typically if you are a 1000ft AMSL you can expect an 85 to 95% (roughly) TQ limit from temperatures of 20 to 30 degrees celsius.
That is your "Takeoff power".

Nowhere in the books is there an suggested limit for the aircrafts nose down attitude. An engine failure with 10 to 15 degrees nose down, before CDP is something I will try with another training pilot sometime. I think with a reasonable amount of inertia in the airframe, that transitioning into a nose up position should be achieveable considering you only have to get to level with the horizon and have 1200 odd feet of run on landing area ahead. Its a lot easier in practice than in actual thou....

Thanks again to all replies....

Steve76 :D

[offshoreigor]

:eek: S76Heavy :eek:

The scenario of an OEI between 35-45 KIAS would require a "quick stop" type manouver ie flair and climb to decrease airsspeed and get back on the normal OEI landing profile, this manouver results in the aircraft at about 30' and 30KIAS then the rest is as per normal 5-10 degrees nose up with a run on landing.

Have a look at the S76 RFM Emergency procedures in Supp 29B, OEI.

Cheers :eek: OffshoreIgor :eek:

[S76Heavy]

OK, Thanks Offshoreigor.
30 degrees nose up, sounds interesting..:cool:
To get back to the original topic: how about starting the initial run with 6 to 10% over hover Tq and when the nose comes up for the initial climb, go to T/O power? Would that make a siginificant difference for anybody?

[Nick Lappos]

S76 Heavy,

I wrote the Cat A procedure for the A back in 1978. It was based on the sea level 90 degree F takeoff, where the excess power from hover (about 78% torque) to takeoff power (about 83%) was small. If the conditions allow 100% torque for takeoff, the acceleration and nose down you have to use are too sporty to be comfortable. The use of 5 to 10% above hover power for the early portion of the Cat A takeoff will work, and does not add distance to the procedure.

Nick

[helmet fire]

Arent we all getting a bit carried away with numbers? We are beginning to sound like fixed wing dicks. :eek: :eek:

Surely you fly the cat A profile (speed/height/attitude/Rate of climb/descent) for your scenario rather than blindly pull a power figure and adjust attitude to cope. Flying the profile is what keeps you alive, and the publication of power numbers is to give you a starting point.

As above, the newer types tend to publish a power margin above OGE or IGE so that those anal enough still have a figure to argue over, those who use judgement to suit the given conditions are still permitted to, and finally those who cannot operate without everything spelled out can still fool everyone into believing they can fly.

But it is ALWAYS the profile that gives you the best chance of getting out of jail - so use it.

[Red Wine]

I guess one has to ask why you would want to use 100%...??

Not only would you have a "Sporty" take off..........also a deck angle that the passengers would write about.

But from the pilots point of view........you would have to be very quick in the OEI situation, as that good engine is already way up there.......not to mention the nose wheel on the runway as you where trying to get the nose back up...

[S76Heavy]

Mr Lappos, thanks for the reply. Only 5%Tq margin, I'm glad I never had to suffer the A..

Helmet Fire, sometimes it's just fun to discuss numbers with fellow aviators. Nothing FW about that.
And as you know, the profile is defined by other numbers as well, so whichever way you look at it, it will always be about numbers.

Red Wine, could not agree with you more. But still nice to know how other experienced pilots feel about the subject.

[Xnr]

Steve

Nice post...

Those check pilots are a pain in the *** eh mate!

See ya soon!

Cheers:D

[Steve76]

Xnr,

Only when they get a few homebrews in the belly and then start ringing other hardworking pilots to harass them and remind them that they are home, drinking, eating and watching hockey.

But even then not really a pain in the arse (more like the neck...:D )

Thanks again MATE.....eh!

Might have some more work for ya soon if ya ask nicely. :)

Make sure you use the ROTOR Brake!!

[212man]

Interesting topic, but it is a bit too late to write much. One point to make is that the accelerate stop distance depicted in the profile is a function of speed at TDP, and not weight ( for all intents and puposes). This means that it is (as said elsewhere) the profile that remains constant, not the absolute power applied. If you are light then you simply apply less power than if heavy. With the same attitudes you should end up at TDP more or less in the same point in space as you would at MTOW using MTOP (or what ever you need for that circumstance).

The weight penalties imposed by lower TDPs (CDPs) on a/c such as the 76 A++ are not a function of the rejected take off space being lower, per se, but of the lower Vtoss that the lower TDP dictates. Obviously lower TDP means lower Vtoss as you have to attain Vtoss within the Cat A requirements, and so (eg) with a 35 kts TDP you can't expect to reach 65 Kts Vtoss before hitting the ground (let alone clearing 35 ft obstacles). You might reach 45 kts though, and this speed with its attendent climb rate dicates the weight, not the distance required to stop.

As an example of the distance vs speed rule, the EC-155 reject distances for varying TDP are the same as the AS332 L-2 for the same speeds, despite the weights being 4,800 kg vs 11,200 kg respectively.

I also agree with the remark about fixating numbers to the extent that the pilot should be able to feel and visualise the procedure by external reference, but only if that is accurate enough to produce the desired figures and therefore meet the required result.

[Iron Hen]

Most fixed wind operators reduce take off thrust to match the aircraft's performance to the field length/ WAT conditions. This is
to achieve longer TBOs for the engines. Works a treat and is an accepted SOP with known thrust decrements applied for each field and set of conditions. Wonder why the helicopter world hasn't come up with a simple reduced thrust reduction for given weights below max CAT A?

[S76Heavy]

We have: hover torque + x%
The debate was about whether that or T/O power gives the best profile.

[Nick Lappos]

S76Heavy,

I think the point wasn't clear enough earlier in this thread. The S76 Cat A procedure in the flight manual is based on takeoff at sea level 90 degrees F, where the takeoff power is only about 5 to 10% more than the power to hover at 5 feet. When you fly the procedure as written at that condition, you must pull takeoff power.
The difficulty that sparked this thread is that when you pull takeoff power at standard temperature (59 degrees F) you have about 25% power above hover power. This makes the acceleration to 35 knots very fast if you pull all that power, and the procedure is abrupt and uncomfortable.

If the power used in such conditions is about 10% above hover power, the procedure is easier to fly, yet still meets the flight manual distances.

Nick

[Steve76]

Continuing the thread on another tack....

Nick, you said the excess power makes the profile fast and abrupt. How would you train someone to fly the Cat A profile?

My description is to pitch up to 15 degrees nose up at 35kts in a positive and authoritive manner. The intention being to transfer the aircraft into the next phase of flight. Post CDP it is the same thought pattern. Move into the next transition with positive and authoritive action and make your intentions to fly away.

Some pilots consider the technique a tad aggressive but generally acceptable. Through experience I have found dithering, slowness or lack of positive action through the Cat A prevents the proceedure from working correctly to give the desired resultant during the engine failure. The aircraft often balloons or labours to fly away if required.

The query here is how would you describe the pilots actions during the profile.
This is a tough question as I have to display it to guys to get them to understand.

Good luck :D

[S76Heavy]

Nick,

perhaps I should have been a bit more elaborate in my previous post. I meant to say that applying a set margin over hover tq (as in 10% in the A+) is our equivalent to downrated thrust in an airliner. But it's also infinately more comfortable when the A/C is light.
But I do believe that the flight manual specifies T/O power for Cat A and the graph shows that that is quite often (in our met. conditions anyway) at or close to 100%

So is it safer to fly Hover tq + x% or pull the lot?
And indeed, how do you train a pilot to fly the profile, like Steve76 asks?

Personally, I like 10% margin and swift rotation, but is there a better way?

[Nick Lappos]

Wow! This thread is a testament to the fact that language is not communication! For both S76Heavy and Steve76:

1) On a cold day, the Cat A takeoff works most easily by using about 10% more torque than hover power.
2) Under the limiting (Hot Day) conditions, when the engine power is least, there is only about 5 to 10% excess power (above hover) whilst doing the takeoff. That is where the procedure was designed, and why it is somewhat uncomfortable at colder days where the power is greater.
3) If you pull full takeoff power in cooler conditions, you have to really exercise the machine to follow the written porcedures, because those procedures were written for hot day.
4) If you pull only 10% torque above hover power on a cool day, the procedure works quite well, is comfortable and will meet the flight manual charts for takeoff dostance and rejected takeoff distance
5) You don't need to pull 100% torque for the procedure to work, try a few during the next training flight, just exercise a land back at CDP while having pulled about 10% more than hover power. You should be able to reject and meet your reject distance anyway. You can just reject on two engines, and land with two, to make the practice safer and easier. Just try to observe your torque on touchdown as being in the ball park for OEI power (about 100% single torque at 826 degrees OEI is like 50% twin torque during practice).
6) If you pull only about 10% torque more than hover power, you don't have to horse the aircraft around and pull 15 degrees nose up just to follow the words in the flight manual. At the slower acceleration, you will more easily capture the 35 knot CDP speed without over shooting.

This is a good thread!!

[S76Heavy]

"Language is not communication"; I agree:)
But now all the parameters have been explained at length, I think the procedure has become clearer to everybody.

But reading back one of your earlier posts you mention "10% for the early portion of the Cat A procedure".
Can you confirm that once past CDP pulling all available tq is a good idea or do you mean even after rotating nose-up at 35KIAS to reduce the time before CDP?

Pardon me for being dense, it's the shiftwork..:D

[Nick Lappos]

S76Heavy,
Yep, pull the moderate power before CDP (when cool conditions make the full takeoff power impractical) then increase to full takeoff power afterward, to climb away from the ground and obstructions quickly.
Try this method on your next training hop, reject at CDP with twin engines and then land back. Note the distance and compare to the charts in the flight manual. Should be quite similar.

Nick

[S76Heavy]

Roger, Wilco :cool:

[offshoreigor]

S76 Heavy

I guess I was not clear in my previous post either. I didn't say 30 degrees nose up, I said a quick stop resulting in about 30 feet altitude and 30 KIAS. A quick stop is defined as any deceleration requiring a nose up attitude in excess of the normal procedures. In the case of the S76 this would be greater than 10 degrees. As Nick pointed out, this will also depend on OAT and A/C weight.

As for the Cat A power required, the S76 RFM Supp 29 B states for Cat A, Hover Q + 6% and Cat B, Hover Q + 10%. As most S76's will require somewhere in the neighborhood of 70-80% Q to Hover IGE, there is no need to adjust power after V2 as you will already be stabilized above 70% which is the accepted minimum climb power for most operators of the S76 or 212.

Just one comment about the A model CAT A profile. Although it may seem a bit agressive to some, it is the the most reasonable trade off of distance available for land back and continued take off. This profile alows a safe land back prior to CDP and in the case of after CDP, (35 KIAS + 55 feet rad alt) a safe continued take off if the Nr is drooped to 96% and VToss (52 KIAS) is maintained. My hat is off to Nick for designing that profile.

I think the bottom line here is to give yourself a loaded deck ie extra power available in the bank incase the preverbial **** hits the rotor.

Cheers :eek: OffshoreIgor :eek:

[S76Heavy]

Offshoreigor, you're absolutely right, I got carried away by my wild imagination.:D
I suppose the reject is similar to our (A+) group B reject, i.e. bleed off the speed by climbing, then land back on.

As far as the profile is concerned, it's certainly safe but not very comfy for the self loading freight..
;)

[John Bicker]

Seem to remember going along as ballast on a training flight moons ago in an A model 76. Cat A clear area. Accelerate/Stop distance and the surface required was about the same for a Twin Otter with the same payload. Also figured out why the T5 repeaters and the ASI is in a funny place as well. So you can see them on the way down as I think the torquemeter became irrelevant. Training was done at high weights with ballast so no fudge factor involved. Have always wondered about the Canadian operations from decks at sea level with pax. Surely must be Cat B departure and arrival.

[Shawn Coyle]

One of the main points about the Category A procedure is repeatability.
That is what drives the numbers and the numbers drive the profile - not the other way around.
The problem is that helicopter pilots are used to only using what is necessary, not like fixed wing pilots who use takeoff power every time.
As Nick says, the procedure is developed for hot, heavy and high as possible, and may need some change for light, low and cool (hey, they all have an 'L' in them).
But just 'flying the profile' is not the answer - the procedure has to be done with the power settings and attitudes to ensure the ability to land safely or fly away to meet Category A.
Otherwise, how is it repeatable?

[GLSNightPilot]

John, I can't speak for the Canadians, but in the US Gulf it's all Cat B. I've been flying helicopters since 1971, both military & civilian, working on 12,000 hours, & I have never done, nor seen, a single Cat A takeoff.

[Steve76]

Shawn,

You are correct. I think it comes down to attitude mostly. All the power in the world will not help you if your mindset during the proceedure is not focused on moving the aircraft from one phase to the other. It is most dependant on good crew co-ordination to follow the prescribed flight path and stay out of the avoid curve.

As far as Cat A off the platforms. I know that the profile is designed with an reject area ( ie: airfield ) so that dictates that anything offshore is going to be Cat B. Generally you are starting with a 100+ ft of altitude as well.

On another similar issue. I have seen a Vertical profile departure that is not designated a Cat A departure. The takeoff is a climb to 100ft AGL and then a 10 degree nose down attitude to fly away. The initiation of the 10 degrees nose down is considered the committed point and subsequently is termed as 'CDP'
Its my opinion that CDP is Cat A terminology and use of CDP in this profile is incorrect. It is not Cat A so a change is vocab is required.
True or False?
:cool:

[rotorque]

False,

CDP terminology is not necessarily a 'CAT A' namesake. It dosen't matter what twin you drive, or in what profile, if you lose a donk prior to a critical point (I will call this the 'Critical Decision Point' :p) you do not have an option.... You must (be forced too) reject the take off.

Cheers

[John Bicker]

GLSNightPilot,

I do vertical takeoffs with accountability in an Agusta 109E Power. Can't call them "Cat A" correctly but "Cat A profile". Cat A after all belongs to FAR Part 29 Transport category helicopters. It will do these profiles up to 3500' DA at gross weight. Of course there are compromises for this performance in other areas.

[Xnr]

Steve76

Two weeks on vacation and this topic is still hot!!

Good One!

Just wondering. For those pilots that want to pull max pwr, why?

I know the profile has limited dimensions but hover Q + 10% does the job nicely.

If I had an engine failure on take off my first choice is to reject if I can. The way I have seen some of the profiles flown lately it seem like the goal is to fly away.

What about the failure post CDP? I am not that crazy about the nose down attitudes either. We already have an altitude of 40' (55 rad. alt.) minimum. Why give it up? Why dive back at the ground? Maintain your altitude, (a slight decent is acceptable if the airspeed is really low,35 kts), adjust your pwr setting, set the Nr to 96% wait for the increase in airspeed ( its not long really)and the subsequent rate of climb.

Just a few thoughts MATE.

Go Leafs Go!;)

[GLSNightPilot]

Of course there are compromises for this performance in other areas.

Well of course there are. And our customers, the oil companies, aren't willing to make them. I don't know about Oz or the north sea, but in the US Gulf, they're only concerned about 2 things:

What's the most you can carry?
When is the latest you can depart?

We take off at max gross most every time, & it's often a struggle to hover, much less do a vertical or Cat A takeoff. We get right at the edge of the heliport, & if it's a 412, hold it steady at a 3' hover until it starts to rise a little, or if a 76, pull 100% TQ & 'ride the bubble' off the heliport, after having verified that we can at least hover. Having the luxury of excess power to do anything else is rare.

[Steve76]

I am still not convinced that 'CDP' is not specifically a Catagory A term. Not trying to say your a dummy Rotorque; but what do others think.

Stan:

Offshore drivers around the globe are nodding their heads in sympathy. Its an unfortunate truth.

Xnr:

My thinking is to get to the better side of the curve. At 35kts and 96% you are really pulling the arse out of the machine and the remaining engine. Closer to 74kts we gain by moving to the bottom of the power required curve and attain advantageous airspeed that can be traded for height (in opposition to gravity) for avoiding obstacles further down the road.
My order of preservation will aways be RRPM, Airspeed and Height in that order. Ya gotta give one to get some of the other, but in the end its the RRPM that will soften the crunch. :D

[Xnr]

Steve76

Are you suggesting that you should trade your 40' (55 rad alt ) for 74 knots?

:(

Keep your altitude , the aircraft will accelerate (if you haven't let it decelerate less than 35 knots in the climb) and if you have calculated your max gross weight for a Cat A procedure. The second you level the nose after CDP the aircraft is already accelerating. Probably in the area of 40 knots +. A dive to gain airspeed is not neccesary.


What kind of obstacle are you trying to clear? Most procedures are designed to clear a 50' obstacle. You already have 40' of that minimum.

BROC is 74 knots at sea level and it does give you your best rate of climb. In that you are correct, but this is for your climb to altitude if you are forced to go enroute OEI, not to clear a 50' obstacle on departure.

Don't get me wrong, I am not suggesting to fly around at 40 knots. Just don't trade the altitude you already have in search of 74. It will come and a positve rate of climb is evident long before that.

If you are facing the CN Tower make a turn.

Just my humble opinion of course.


;)

Cheers Mate

[rotorque]

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 :D

[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 :)

[S76Heavy]

Is Vtoss 65 Kts a CAA thing or is it worldwide?

[Xnr]

Vtoss on an A model is 52 knots.

Cheers

[S76Heavy]

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?

[Nick Lappos]

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.

[Xnr]

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

[helmet fire]

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.;) ;)

:)

[Xnr]

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

[John Bicker]

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?

[Xnr]

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

:)

[Steve76]

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

[Nick Lappos]

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.

[Q max]

!