Question about turboprops

[E1453]

I'm about to start the transition course from the venerable Bonanza A36 to the Piper Cheyenne or the Beech King Air.

Although I've studied a lot about jet aircrafts and it's systems, I know little or almost nothing about turbopropellers.

The one thing that intrigues me the most is the pressurization controls at the King Air, as I've seen in pictures. It's seems to lack any automation at all! It's worst than the 737-200 pressuruzation controls, even the B200 or the B350.

How this system works and why it still made this old-fashioned way?

Thank's for any responses!

:ok:

[OzExpat]

If I were to invoke haiku for this, I'd say that it is because it is. And that's about the whole story. I don't know how old you think Kingairs are, but the fact is that its' pressurisation system was, like the aeroplane itself, not made yesterday.

Personally, I've never had a problem with the functionality of the system and really fail to understand why this seems such a problem. I set the pressurisation control to where I want it and monitor cabin climb or descent, and the differential, to make sure everything happens the way it should. Once I've set it, the system actually IS automatic in that it will take the cabin to the desired cabin altitude and maintain it for me.

All I have to do is watch to make sure it happens. And, of course, I need to know what to do about it if it doesn't happen.

[E1453]

Thank's for you response.

The fact is I've never been on a King Air or Cheyenne, and I don't have the manuals yet.

Looking at the pictures of the King's cockpit, I saw the pressurization panel I found it odd. I'm so used to the Boeing 737's systems (wich I learned during my graduation) that I thought the King's system odd.

Otherwise, could anyone explain me what is King's or Cheyenne's performance capabilities in case of a engine failure on takeoff? I'm know the FAR Chapter 25's rules, but never saw the requirements for turboprops in general aviation.

Thank's!

[vunzke]

Hi E1453,

Performance wise the King Air is a beautifull plane as it is in every other aspect. I've done about 2000 hrs on it in VIP charter and loved the plane. Single engine performance is great and with the rudder assist (also a very basic but non the less effective system) a very pilot friendly aircraft.

Id say, sit back and relax, listen to you instructor and study the books and youll enjoy the ride from the first flight on...

have fun

[OzExpat]

Yeah, I've got a few thousand hours on Kingairs, C-90 :yuk: and B200 :ok: The latter is what I refer to as a gentleman's aeroplane. It is a very versatile aeroplane indeed with good slow speed performance that's got me out of a few difficult situations. In one instance, due to an ATC stuff-up, I ended up at 10,000 feet at 10 DME on approach and was able to rescue the situation with a 1:1 descent profile very nicely.

I have an idea that, after a particularly nasty prang on take-off from Sydney, involving a B200, many years ago some flight tests were conducted. If my aging memory serves me correctly, the tests found that. at MTOW in given conditions (and with a pilot who was ready for it), an engine failure prior to V1 could be negotiated without rejecting the take-off. That is, the aeroplane actually accelerated to V1 on one engine and got airborne, then flew a circuit and landed again.

Clearly, not the sort of thing to explore too closely, but an indicatuon of just how good the aeroplane really is.

I've enjoyed all my B200 flying immensely and can recommend it to you very highly. As vunzke says, "sit back and relax, listen to you instructor and study the books and youll enjoy the ride from the first flight on". I'm sure that you'll enjoy this very forgiving and flexible aeroplane. :ok:

[E1453]

Do the King Air have a published V1, VR and V2 for each weigh & temp?

In case of a engine failure at V1, will the King overfly the runway end at or above 35 ft?

What V1, VR, V2 and VREF is common to use?

Can you use reduced thrust (or assumed temperature) on takeoff?

Any problem in reducind prop rpm first, before reducing the torque, at the first reduction after takeoff?

Sorry for asking so many questions, but thank's for your help.:ok:

[604guy]

Pressurization controls on all Kingairs (except perhaps for some early A90's) are extremely easy to operate. The same can be said for Cheyennes again except for some early II's. In the early models of those you have to select cabin altitude and then after takeoff select ascend, neutral at top of climb and then when ready for descent, reset cabin altitude and select descend. Not likely you'll run into that unless you get into something manufactured mid70's vintage.

There is not really anything to gain in using reduced thrust takeoffs in this catagory of aircraft and might get you into a bad situation one day if Mr Murphy raises his head and you have an engine loss as the gear is going in the wells.

If you reduce prop RPM first after takeoff without reducing torque first you will almost certainly exceed torque limlts. Torque will increase as you reduce prop RPM.

[compressor stall]

From the 200/200C POH. Note these are not Raisbeck modified KingAirs!

When looking at the figures remember that you are dealing with an FAR23 certified aeroplane. In a nutshell all it is required to do is maintain a positive rate of climb on one engine up to a certain height.

Beechcraft offer the computations and charts for a balanced field length. They state that it is possible to reduce weight to "obtain the performance specifications of FAR 25 during the critical takeoff and initial climb segments. ...full compliance with other regulations applicable to FAR25 is not implied." It is quite an involved process and a lot of iterative calculations need to be performed.
(the example they use is on a hot day at 5000' field, 2+kms of rwy and 10 kts headwind, you need to limit your weight by 2000 lbs below MTOW!)
So the following answers deal specifically with non FAR 25 charts

Do the King Air have a published V1, VR and V2 for each weigh & temp?
They publish a rotate speed and a 50 foot speed for different weights (Vr is always 95kias and 50' is 121@12500 down to 108kias@9000lbs.
V1 equals Vr according to the notes.


In case of a engine failure at V1, will the King overfly the runway end at or above 35 ft? Refer the charts and the comments above. If light yes, it should.

What V1, VR, V2 and VREF is common to use?
See above figues. Approach Speed (they don't use the term Vref) is 103kias@12500lbs down to 93@9000.

Can you use reduced thrust (or assumed temperature) on takeoff?
Why would you want to make a performance that is marginal even more so?

Any problem in reducind prop rpm first, before reducing the torque, at the first reduction after takeoff?
Yes - your torque will go though the limits. Takeoff torque @ 2230ftlbs . RPM @ 2000. we reduce to 2000ftlbs and 1900 at first power reduction (LSALT at night/IMC). To easiest procedure is reduce the power to 1900ftlbs and then pull the props back to 1900rpm. The torque will rise to about 2000ftlbs then and only small change necessary to peg it exactly.
A lovely machine to fly. A tad thirsty perhaps, but a new Kingair climbs out like a homesick angel. As for the pressurisation - it's pretty simple really. Before t/off set the pressurisation controller to the cruise alt plus 1000 and before TOD set the airfield elevation plus 500' (there is a chart to be more specific if you must). Wind it slowly to begin with to avoid cabin drop, but it works fine. Smoother than the PC12's pressurisation controller! :ok:

[E1453]

Sorry for asking, asking, asking, again and again!

Does the manual say the King will fly, after an engine failure at rotation, at standard day, with MTOW?

Is there a takeoff chart with the Performance-Limited MTOW for runway lenght, slope, temp & elevation?

What the FAR23 says about single engine performance on takeoff for King-like planes?

I though it would be interesting to reduce temps with a reduced power takeoff, to save the hot section of the engines. If there were takeoff charts like the ones on Boeing's manuals, with field limited and climb limited performances, we would be able to calculate engine power to meet at least FAR 23 requirements, when not fully loaded.

What do you think?

[OzExpat]

I suspect that you might have misinterpreted my previous post. The B200 Kingair is not a FAR25 aeroplane. Therefore you cannot think about it in those terms. The incident to which I referred in my previous post occurred because, it is alleged, that the pilot used a reduced thrust take-off technique for noise abatement purposes. It is generally assumed that he believed that there was sufficient runway length for that and, indeed, that was probably true... if and only IF nothing went wrong during the take-off.

Well, something went horribly wrong.

It is never a good idea to consider reduced thrust in any aeroplane of that class. There is nothing to be gained by it as the noise footprint is far less, even at max take-off thrust, than the average jet. This, of course, is simply my own opinion, but I feel sure it is a widely held opinion.

There ARE performance limitations but, for take-off, they mostly resolve into the clash between torque and temperature (ITT). At least, that's the case in my experience. We have SOPs that say that, if we have 1000 metres of runway up to about 1,000 feet elevation, we can go at MTOW and still meet balanced field length considerations.

I operate in the tropics where the average temperature is between ISA +15 and ISA +20, so an elevation of 1,000 feet can produce a density altitude of around 2,500 feet. I operate into aerodromes up to 5500 feet AMSL (some operators take B200s in and out of airstrips at much elevations) but we have SOPs to deal with the reduced take-off weight.

The performance limitations based on runway length and associated environmental conditions are related to take-off weight. These charts always assume that you will use the ITT and torque associated with the conditions. To that extent, yes, there is an argument concerning reduced take-off thrust, but I think you need to read the Manual to understand it.

The B200 is not a Boeing. I can do no more than to strongly recommend that you study the Manual, believe it, but add a fudge factor to ensure that you can enjoy a beer at the Aero Club after each flight.

It is a great aeroplane and a very forgiving one, but it DOES have its limitations, just like every other aeroplane. If you follow all the good advice that has been offerred so far in this thread, by all those who have replied, you'll enjoy flying the aeroplane. Just, please, please, please, consider it as more of a GA type aeroplane than a Boeing.

In fact, if you forget all about the Boeing, you might be better off. That way, you can explore its' performance gently, in a more controlled and professional manner, and find out for yourself what it will do for you when the chips are down.

The post by my good mate compressor stall is spot-on, so I recommend that you take a copy of it for reference in your training.

[compressor stall]

You might want to study these links.

FAR 25 (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/CurrentFARSubpart?OpenView&Start=1&Count=200&Expand=6.2#6.2)

FAR 23 (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/CurrentFARSubpart?OpenView&Start=1&Count=200&Expand=5.2#5.2)

Of course just open and print the relevant bits. Place them side by side and understand what FAR 23 does NOT say.

CS

G'Day OzEx what's to go with the geography movement? you got a new job or sumfink? :8

[E1453]

I read the FAR23, about commuter planes. Very enlightening.

Well, please correct me if I'm wrong, but I think the T/O performance for a King-like (commuter) turboprop is:

T/O runway requirements:

2 engines running: 115% of the distance required to climb to 35ft at not less than V2

1 engine running: the distance required to climb to 35ft, at not less than V2, in the case of a failure after V1, of course

climb requirements:

gear down, runway level: must demonstrate a measurable climb, T/O power & T/O flaps, not touching the engine levers

gear up: 2% climb gradient up to 400ft, T/O power, T/O flaps, not touching engine levers

above 400ft up tp 1500ft: 1,2% climb gradient, MCP, flaps up

Well, thanks for the advice, compressor stall. It did help a lot.

I can now figure out that the capabilities of commuters are not comparable to those of transport jets. It's impossible to comply with any SID's climb gradients. For me, the most critical moments would be beetween the liftoff and the gear retraction. I can imagine the consequences of a propeller failing to autofeather.

:8

I forgot to mention:

Knowing the marginal performance beetween liftoff and V2, I know realise why you folks don't recommend any power reduction at T/O. Before retracting the gear, it may be hard to keed this baby flying! Every single horse would help a lot in such a situation!

Thank's!

[Tinstaafl]

Why do light twins , including commuters, have two engines? Because they need BOTH of them.

At best they're the equivalent of a single engine a/c with half its engine mounted 'over there' and the other half mounted 'over here'. This means that an engine failure is constrained to be more like a 'partial' failure of the (single) engine.

Like single, a partial failure may leave you with enough power to maintain flight......or it may not. Instead of having sufficient excess of power to guarantee performance (two engine or FAR25 a/c) you're now in the situation where you just barely have enough **IF** the a/c is configured optimally. BTW, gear down, flap down & prop windmilling is not 'optimal'....

[OzExpat]

I'm glad that there's been enough help for you, E1453, in understanding what the aeroplane is certified to do. Having a healthy respect for it will help to ensure that you enjoy the time you spend flying it. :ok:

stallie... no such luck mate. It's just a two-month swan on expenses! Nothing less than I deserve, of course! :E

[E1453]

I have a few more questions:

I know that the RPM has an effect on torque, just like the real engines (the reciprocrating big bores are more fun!), but, is there any effect of RPM on TIT?

What's the best condition for cruise, in terms of engine management? It includes: fuel efficiency, engine longevity (low temps) and noise.

I never saw an turboprop power chart, but I would like to know the best combination of torque x RPM to achieve the above results. Surely RPM's leads to low noise levels, but is it good to fuel efficiency? Is it good for engine longevity?

Does the use of de-ice devices reduce the engine power (propeller output, to be more accurate) significantly?

Thank's in advance!

I have a few more questions:

I know that the RPM has an effect on torque, just like the real engines (the reciprocrating big bores are more fun!), but, is there any effect of RPM on TIT?

What's the best condition for cruise, in terms of engine management? It includes: fuel efficiency, engine longevity (low temps) and noise.

I never saw an turboprop power chart, but I would like to know the best combination of torque x RPM to achieve the above results. Surely low RPMs leads to low noise levels, but is it good to fuel efficiency? Is it good for engine longevity?

Does the use of de-ice devices reduce the engine power (propeller output, to be more accurate) significantly?

Thank's in advance!

[Sheep Guts]

Gday E1453,
Well good posts sofar all the B200 Gurus(OzExpat and Stallie). Im not one,maybe a A90 Guru and a Twotter hacker. But mate generally engine wear with Turbines is done during start up and shut down. You have to take note of the Limits in ITT, and stick to them, but not use them as a power setting (as some people). For example on a A90 the Max continous ITT in the cruise is 705. Now thats a limit , never set it in the cruise.

Also monitor and record you start temps. The limitation we know for all PT6s is 1090 for 2secs. And not to add fuel unless you have a sustained N1 RPM of 12 %. Well ill tell you it will start at 12%! But man your gonna get a really exciting start temp from that. The trick is to recognise this before adding fuel, could be bad GPU, Battery or Startergenerator. Youll here it spin up alot weaker and you may notice the Bat volts get loaded down t0o much. If it is abort the start and get a tech to check it out , dont add fuel, or you get a start , but you may shave many hours off a good engine. Every engine temp spike contributes to blade and Hot section damage over the long term.

Funny thing, people talk about reduced power take offs in Turbo Props. A definition of this, maybe needed. Basically we all do reduced power takeoffs, especially in the Tropics because we get to Our ITT limit much more easily, due to the increased ambeint Temp. When I I flew Twotter -200S WITH -20 engines we had 90% power takeoff cards that we used to set the TO Torque with OAT and TOW, if I am recalling basically it was the same input as on the Torque computer which Dehaviland supply with all their Twotters.

We would have reduced torque settings. If there would be a setting for 2 engines and one for 1INOP which was alittle higher.

Ofcourse when I moved to -300Twotter the temps limits were still there but the engines were alot more accomadating.


Yes bleed air effects power output. But only slightly. With nothing touched after turning on bleed air you notice a slight reduction in torque and slight increase in FFlow.

Fuel efficeincy you will get better with altitude ,just like your 737, no difference really. And the most optimum will be very close to your Max ITT Cruise limit incidently.

When I level off at around FL200 in my A90, I set up the props to 1900 RPM as specified. But if I forget to bring back the RPM to 1900 from 2000 then Ill notice small diffference in Torque and Fuel flows. AT 2000 RPM for a given torque setting I get a a higher fflow than for say 1900RPM. Why you ask? Well its designed for it the Reduction Gear Box and the mutlitude of test flight hours done by the Beech People got the optimum setting. All the Crusie Power Tables in A90 Manual anyway use 1900PRM.


Anyway enough of my blithering

Hope it helps

Sheep:ok:

Yep Ex A90s and C90s are :yuk: , but hey thats what all the other ones got their genes from.:ok: