Reduced power take-off's in King Air and other turbo-props.

[A37575]

Regarding King Air turbo prop types. To be legal should full power be used for all take-offs? In other words are reduced power take offs legal?

I ask the question because some operators of aircraft such as the Bandeirante, and King Air use less than full rated power in order to avoid inadvertently exceeding the maximum take off torque.

This has the effect of extending the take off distance required and also risks the chances of an over-run in the event the take off is aborted before gear retract. I thought only turbo-jet aircraft were certified for reduced thrust take offs and then only under certain circumstances.

[gaunty]

No, non, nyet, nada, nein there is no LEGAL basis nor are there any certificated charts that allow TO with reduced power.

Max torque or temp which ever comes first.

Depending on the condition of the compressors and/or the temp/elevation you might go temp limited first, but the parameters required for the day will be in the WAT charts in the book.

But then CASA have approved some really odd things in Ops Manuals over the years.

If this is a "mandatory unofficial" requirement just keep practising your skills in handling hostile cross examination in a courtroom and perhaps being made personally liable for the damage.

[Spotlight]

The salutary example provided by Advance Airlines (if memory serves me correct) at Sydney twenty odd years ago must have passed from collective memory. It hit the sea wall killing all on board. EFATO.

Other factors as well, including autofeather disconnected on the two Kingairs that had it out of the fleet of three for purpose of standardisation. Unfortunate as the crash A/C was equipped.

Also unfortunate was no headset, requiring the use of a handmike during assymetric flight and a lot of back and forth with the controller due a 727 landing negating a 180 deg return to the R/W

A BIGGY in the BASI report though was the use of reduced power T/Os.

[splatman]

Gaunty,

I hate to disagree with you but manufacturers have approved the use of reduced power for take off in a number of turbine aircraft types that I have been involved in.

The basis is that of utilising an assumed temperature for your take off.

In a simple form it works like this, if the aircraft is capable of meeting all runway and performance requirements at a specific weight - say 5700kg and an ambient temperature of say 40 degrees, but the actual temperature is only 10, then take-off power can be reduced to that of the power setting that would have been utilised on the 40 degree day (reduced a maximum of 10% usually)

The logic applied here is that the power setting used on the 40 degree day will meet the performance requirements if it is used on the 10 degree day.

ie - Use the power setting that will obtain the required performance within the manufacturers minimum limitations. After all, if you need the additional power it is always available and the saving by way of engine costs can be significant.

[ITCZ]

You can use reduced power takeoffs in a Metro 23 via the Assumed Temperature method (described above by splatman). I think, but am not sure, that it is available in the EMB120 Brasilia.

I hasten to add that you just can't decide that reduced power takeoffs in a turboprop are a good idea. You can't mess with your power without considering TORA TODA ASDA balanced field and climb performance.

It has to be in the AFM, giving both performance data and specifying the techniques and crew procedures to follow. It also has to be written into your ops manual and your pilots have to be trained and checked on how to do them.

[jarjar]

I hasten to add that you just can't decide that reduced power takeoffs in a turboprop are a good idea.

I agree, every company is different however.Why not use max available for Take off and then use a reduced cruise and climb setting, much safer. There are significant extensions in engine life to be had by using reduced torque, temp settings AFTER TAKE OFF.

[Spotlight]

splatman, you may well be right. To use assumed temps etc the operator would need to be using RTOW tables meeting the reqs of CAO 20.7. 1B and CAR 235. That is runway length and segment obstacle clearance.

It is not clear in the first post whether this is the case or not.

[gaunty]

splatman please feel free. :ok: bit quick on the draw there. :O
You're right, but as ITCZ says there are a whole bunch of qualifications.

I was referring to regular ops in FAR23 types maybe SFAR23/41 types have it available, certainly it is for FAR25 types.

Like Spotlight I'm dredging my memory on the Advance accident, and if my memory serves me correctly there were some very red faces in the regulator and their surveilance on it.

The assumed temperature case also means that you are denying yourself the "extra" runway and obstacle clearance when you really need it.

I can't recall if it was the same accident but a failure to increase power to the maximum available on the remaining engine was a contributory factor.

IMHO in single pilot ops trying to sort the deadun and get cleaned up and going is busy busy without having to reset the live un and you're off the back of the curve all the time.

With carefully and properly trained and supervised pilots we never found it necessary, nor did we ever have any surprises at HSI or overhaul.

[pakeha-boy]

gaunty...believe you are wrong on the reduced pwr t/o,s ...have used them for years on the metro/dash 100/200/7...King air 200b....this has been a hotly debated issue and has been ultimately been the decision of the company involved.....obviously factors ie density altitude etc dictate your pwr setting,but reduced pwr setting have been around awhile......pilot participation is your choice.....currently on the A320(jets vs Turbines)...we are able to flex up to 25%....we are actually required to do this......kia kaha

[Gravox]

Reduced power take offs reduce the EGT and therefore increase the life of the engine.

The company I flew metros for used the assumed temperature method for reducing power. However I knew a lot of the chaps didn't like doing it and used max power available instead. If using performance charts for the specific runway in use using the assumed temp method will ensure that all climb gradients are adhered to. However the standard procedure following an engine failure is gear up and max power which gives you that little bit more. The metro was only allowed to reduce power by a maximum of 10% torque.

[compressor stall]

In an aircraft that is only certified to FAR 23, (the KingAir which is the primary subject under discussion) why on earth would you want to?

I suggest you all read the accident report of the C90 accident at YTWB.

An engine failure at the wrong time, do everything right and you are still going down. Why make that window any longer?

Transport Cat/FAR 25 aircraft are a different kettle of fish. "Guaranteed" performance, 2 pilots, NTS etc etc etc.

Reduced hot section wear means jack when you are through the fence off the end, or worse.

[The Messiah]

Regional turbines such as Dash/Saab/Bras etc do it all around the world and are totally legal.

As for terrain clearances on one, if the aircraft is certified accordingly then MCP on the live engine will keep you out of trouble. That is assuming it is operated by a 'competent crew'.

[gaunty]

Folks I think we are probably probably all in heated agreement on one issue or another.

As Stallie IMHO quite correctly points out it's the old certification issue.
FAR23.....SFAR23/41......FAR25

SAFE....SAFER...SAFEST

Different strokes for different blokes.

ITCZ as he often does says it much more eloquently than I.I hasten to add that you just can't decide that reduced power takeoffs in a turboprop are a good idea. You can't mess with your power without considering TORA TODA ASDA balanced field and climb performance.

It has to be in the AFM, giving both performance data and specifying the techniques and crew procedures to follow. It also has to be written into your ops manual and your pilots have to be trained and checked on how to do them.

IMHO though" conceptually legal by regulation" (and I speak of FAR23 types) it may be, I suspect it is not something the manufacturers would support without a black letter law certification rule setting out the certification performance requirements for it.

Even so IMHO this is a dubious practise given the risks that the PIC will fcuk up weighed against the so called costs savings.

It takes as much care to properly and legally set the flex power as it does to set full power, otherwise why bother and it simply introduces another action to be performed exactly when you need the most concentration to save your sorry ass in a machine that wasn't certified for the FAR25 "guaranteed" case in the first place.

I can hear the posters revving up now to tell me that the Whizbang123 turboprop goes up like the proverbial on one, I'm here to tell you you're in for a nasty surprise one day.
At best around 220fpm and then only when you're "slotted, feathered, clean and tidy" and holding your mouth the right way. :)
On the other hand in general terms for FAR 25 performers, besides "positive rate gear up", ALL other items beyond flying V2 are left for review and action until the third segment.
And of course there's the old multicrew argument to add to the confusion.
Am I correct in making the following statement?
The assumed temperature case also means that you are denying yourself the "extra" runway and obstacle clearance ( I should have added "available" here) when you really need it.

[J430]

Here is another to add to the list of most useless things in aviation..... The runway behind you, the height above you, the space in your fuel tank and the "revs / torque" you didn't use on takeoff.

J:ok:

[Cloud Cutter]

Not really, if performance criteria are met. It may well save you an engine failure on subsequent flights.

[jarjar]

I can see that this topic will dribble on for days possibly weeks, maybe months. How about we all agree that, Yes you can use reduced power/torque takeoffs, and that some operators approve their crews to use it, yet the choice remains solely with the operating crew on the day.

[splatman]

Obviously some strong opinions on the subject and that is always good when people think about performance.

But wasn't the original question " is it legal?"

OK - I think we have worked it out - YES IT IS! :D

[prospector]

"Is it legal"

For the reason put forward, "inadvertantly exceeding max T/O torque" maybe and maybe not.

The numbers required are not easy to come by for part 23 aircraft. So for my money, go for max and monitor gauges.

Prospector

[Centaurus]

My understanding is that the RFDS at Essendon use the technique of using slightly less than full power than max on take off in order to minimise the possibility of inadvertent exceedance of full power. On the face of it this sounds a reasonable argument. But really, this is only a bastardised form of reduced thrust take off without the formal use of a runway analysis presentation.

If an engine fails and rudder is used (of course) to stop further yaw, then by increasing power on the live engine back to that additional torque, the yaw will be increased and could catch the unwary. One presumes of course that CASA has approved the policy described above. If so, the buck stops there - maybe?

Let's face it, the whole business of not using the manufacturer's recommended technique in this case could be perfectly safe on nice long runways, but although I am not licenced on type, I find it hard to imagine it being a manufacture's recommendation. If that is correct, then as Gaunty pointed out, watch out for the legal fraternity who would quickly swoop if there was an accident in which reduced throttle setting may be a factor.

[jarjar]

My understanding is that the RFDS at Essendon use the technique of using slightly less than full power than max on take off in order to minimise the possibility of inadvertent exceedance of full power.

It is common practise to set a slightly lower torque(static), to allow for the ram rise as speed increases and the aircraft gets airborne. My understanding of the Pt6's is that the 2230ft lbs max torque is set below the gearbox limit not the engine limit(engineers pls comment). If you consult the Afm on say a Kingair 200 (-41 engines) it states that the max torque value is 2750 for maximum of 5 seconds. It is interseting to note that the torque limiter is set to reduce fuel flow and hence torque between 2368 and 2447 ftlbs, this could be interpreted as the gearbox limit(and is stated so in the afm) at which damage could occur. it is very unlikely that exceeding 2230 on takeoff by 10lbs is going to cause any damage(if you can read between the lines on the guage that clearly)especially with limits as high as what Ive stated(once again engineers pls feel free to comment).

What Im trying to say is why not just go for max torque

:ok:

[compressor stall]

There's a BIG difference between:

1: setting 2050ftlbs and allowing ram rise to take it up to 2230ftlbs during the take off; and

2: doing a reduced power take off (having a max pwr of say 2000ftlbs during the takeoff phase.

(talking about a B200 here).

CS

[jarjar]

There is another thing that we must all consider if using reduced thrust for take-offs in a King air and that is the affect it MAY have on the operation of the autofeather. Even though you check the armed annunciators after initial power application, if you are using a reduced thrust setting, if there is even a slight movement rearward of the power levers it may prevent the auto feather from operating normally in the event of an engine failure.

On the SKA 200,B200 the autofeather is armed(if the switch is in arned position) as the power levers are advance beyond 90% N1.This 90% setting is calibrated on power lever position, not on an absolute value of 90%(ieon the gauge)(eg autofeather may arm at 88% or 92% based on an average position where the power levers would attain 90%-hope people can understand my dribble).

Now, in the event a reduce torque take-off is used there may not be a huge margin between the position of the power levers at the reduced torque setting and the 90% value for the operation of the autofeather. The chance that a power lever may creep back after initial setting of power does happen, regardless of how tight the friction nut is.

Once again I hope some engineers can comment to put it all into perspective.

JarJar:ok: