Cheyenne 400 VS King Air 200

[bigD]

Why would you want a turbo prop that is RVSM qualified. If you are operating at 28,000 and above, you are either in the wrong aircraft for your mission or you don't understand the performance curve of a turboprop.

I think in the case of the 400LS - the fuel burns get pretty reasonable in the mid 30's. I've heard numbers like 340 knots on 500 pounds per hour up there. That's pretty impressive, given that I burn that much gas on 80 fewer knots in the 20's.

 

[THE Flying Ace]

In the old Citation II, we are lucky to do 340 kts in the mid-thirties and we are burning double what the 400LS is burning.

 

[FlyFlyFly]

you don't understand the performance curve of a turboprop

From the numbers I have seen, the airplane doesn't have a good understanding of the performance curve you reference either.

Maybe you could sit it down and calmly explain things to it...

 

[Thedude]

I think in the case of the 400LS - the fuel burns get pretty reasonable in the mid 30's. I've heard numbers like 340 knots on 500 pounds per hour up there. That's pretty impressive, given that I burn that much gas on 80 fewer knots in the 20's.

340 TAS ?? That seems a little high

Have you looked at the specfic fuel consumption...just because your fuel flow goes down doesn't mean that you are getting the most bang for the buck. I dont know a lot about the K-Mart King Air but I understand it has Garretts. I have many hrs in the TPE-331-12 and I can defintly tell you your power available curve really drops off after about 18,000'. So unless you are looking for max endurance you should stay in the mid teens. Same goes with the King Air.
I am trying to find the performance curves for the SA-227 and the BE-200 in my library but it is all in boxes right now

 

[bigD]

340 TAS ?? That seems a little high

That's what was told to me by a guy that flies one, but he could have been BS'ing me - I dunno. I don't have any personal experience with the 400LS, I was just relaying a data point from someone who would know.

 

[Thedude]

I found my old BE-200 manual right off the bat. And luckily it already has the TAS curve and the range curve already calculated.

if you look at the cruise speed chart you will see tha the TAS curve is linear until 14,000 @ 284 TAS then it does a small regressive curve and peaks at 23,500 at 286 TAS.
14,000 wil give you a range of about 1120 NM @ 281 TAS
23,500 will give you a range of about 1380 NM @ 286 TAS
35,000 will give you a range of about 1900 NM @ 259 TAS

Assuming no wind, the best opearting altitude would then be 23,500 for best dist. vs time. Remember you also have to look at time to climb, descend and stage length. Typical length for a turboprop are 1.5 hrs and shorter or about 500 NM. If you are operating more than 500 nm its actually cheaper to switch to a jet.


I did a couple of quick calculation of a flight for 500NM
At 35,000 its 2:03 with a burn of 1021
At 18,000 its 1:50 with a burn of 1364
a slightly higher fuel burn at 18,000 but the stage length is very long for a T'prop

 

[jasonwb]

Why would you want a turbo prop that is RVSM qualified. If you are operating at 28,000 and above, you are either in the wrong aircraft for your mission or you don't understand the performance curve of a turboprop.

for the most part this is true, but the King Air 300 is one of the few TP's that is a great performer in the low 30's. it will true 300 kts at almost every altitude you choose to fly at. the TAS really doesnt bleed off until you get to around FL320 and up and your fuel flow is significantly lower in the 30's.

jb

 

[CL604DRVR]

for the most part this is true, but the King Air 300 is one of the few TP's that is a great performer in the low 30's. it will true 300 kts at almost every altitude you choose to fly at. the TAS really doesnt bleed off until you get to around FL320 and up and your fuel flow is significantly lower in the 30's.

jb

I agree with that. I used to get 290 true 600pph @ 350 in my King Air 350.

 

[cvsfly]

I found my old BE-200 manual right off the bat. And luckily it already has the TAS curve and the range curve already calculated.

if you look at the cruise speed chart you will see tha the TAS curve is linear until 14,000 @ 284 TAS then it does a small regressive curve and peaks at 23,500 at 286 TAS.
14,000 wil give you a range of about 1120 NM @ 281 TAS
23,500 will give you a range of about 1380 NM @ 286 TAS
35,000 will give you a range of about 1900 NM @ 259 TAS

Assuming no wind, the best opearting altitude would then be 23,500 for best dist. vs time. Remember you also have to look at time to climb, descend and stage length. Typical length for a turboprop are 1.5 hrs and shorter or about 500 NM. If you are operating more than 500 nm its actually cheaper to switch to a jet.


I did a couple of quick calculation of a flight for 500NM
At 35,000 its 2:03 with a burn of 1021
At 18,000 its 1:50 with a burn of 1364
a slightly higher fuel burn at 18,000 but the stage length is very long for a T'prop

Operating a B200 with -42 engines book calls for normal cruise at 1700 rpm, ISA - TAS peaks at 22,000 at 281 K and flow at 674 lbs. At 18 k TAS is still 280 and burn at 746. This all based at 11,000 lbs. This the table on Page 5-55 vs chart on pg 5-60 which gives slightly higher speeds. The table is pretty much on the mark in our experience. Of course we hardly ever see ISA or standard lapse rates. We normally pull 2050-2100'-lbs until we get 750 ITT (vs 800 max) (using these numbers we usually temp out around 16 -18k) and try to get to 24,000 going and 25,000 (typically :15 - 17 min un obstucted climb) coming home depending on winds and get 270 kts in summer and 275 in winter with about 600 - 650 lbs/hr. Good rule of thumb for altitude vs stage length for us is - distance x 100 = altitude up to ideal of 250 nm = altitude of 25000'. Less if expecting STARS or SIDS that keep the TPs down low anyway.

 

[Thedude]

for the most part this is true, but the King Air 300 is one of the few TP's that is a great performer in the low 30's. it will true 300 kts at almost every altitude you choose to fly at. the TAS really doesnt bleed off until you get to around FL320 and up and your fuel flow is significantly lower in the 30's.

jb

I have never flown a BE-300 but i think that is the same as the B-1900? If it is I have a hard time belieing that it will hold 300 TAS up till the 30's. The reason I say that is, I used to race a 1900 against a Metro (me) and the metro would usually win.

Then again it might be because the BE-300 weighs considerably less than the 1900. There are a few T'props that do defy the conventioanl t'prop performance such as the Saab 2000. Mainly because that have plenty of SHP available.

Then again I haven't flown a t'prop since '99 and the rules for jet performance are a little different.

Doing a cruise climb has to be one of biggest peeves that people don't do. They aim for something around Vy and never condsider the additional mileage they could have covered if they would climb at a higher airspeed. As a general rule for t'props, I never went abve 18-20 range unless the winds were really cranking. You just loose to much time in the climb and TAS vs what you save in fuel flow.

Like I said before, most guys just don't understand the power curves for a T'prop and its mainly because they have never been taught to look at such items and compute the climb and descent profile.