Turbo for flatlanders

[Morne]

I totally understand the desire for turbo amongst the big rock crowd. High DA conditions in the summer when you want to haul the family on vacation make it a good choice. But what about for us flatlanders? Is there call for turbo east of the Mississippi?

My instructor is teaching a guy who bought a T182. The guy flies from here in Ohio to the Carolinas, Chicago, places like that. Nowhere that REQUIRES a turbo, but obviously with one you can go higher/faster. My question is, "Is it worth it?"

Certainly there is some added maintenance with a turbo. Is the added maintenance cost something that completely changes the equation for ownership or just a minor tweak? Do engines die sooner with turbo or is that a function of how well, or poorly, the pilot utilizes it?

Just generally trying to wrap my head around turbos and folks wo have them, but don't NEED them, for their flying mission.

 

[wabower]

Based in KC, I operated a 210 for 7 years and several thousand hours and then a T-210 for 19 years and even more hours. IME, your analysis is accurate. Nice to have, perhaps, but no real need to have unless the plane is also FIKI and you plan to get above some of the stratus ice.

You can operate NA airplanes at higher altitudes, and you can safely fly in the rockies without a turbo, but both require more time to plan and execute.

I totally understand the desire for turbo amongst the big rock crowd. High DA conditions in the summer when you want to haul the family on vacation make it a good choice. But what about for us flatlanders? Is there call for turbo east of the Mississippi?

My instructor is teaching a guy who bought a T182. The guy flies from here in Ohio to the Carolinas, Chicago, places like that. Nowhere that REQUIRES a turbo, but obviously with one you can go higher/faster. My question is, "Is it worth it?"

Certainly there is some added maintenance with a turbo. Is the added maintenance cost something that completely changes the equation for ownership or just a minor tweak? Do engines die sooner with turbo or is that a function of how well, or poorly, the pilot utilizes it?

Just generally trying to wrap my head around turbos and folks wo have them, but don't NEED them, for their flying mission.

 

[Ted]

It's a personal flying preference. Turbos will typically require you to fly at or above 8,000 ft to get a benefit in speed. If you fly low all the time, your benefit is increased maintenance cost.

However, if you can gain 10-15 kts by flying at 15,000 ft. vs. 6,000 ft and do so, then that means you're going, say 8-12% faster, then that reduces your cost per mile for the plane, which can offset the cost of the turbo. We've figured that on the 310, turbochargers would break even for us cost wise while allowing us to get the job done faster.

 

[Alexb2000]

I am a BIG fan of turbos. I can't even count the days I hear all kinds of GA traffic down at 4-8K in the bumps and weather when I'm cruising above it all.

In the winter, ICE, I couldn't operate many days without a turbo. Getting on top is key to avoiding some bad encounters with ice. Having a turbo makes that much more possible.

Florida afternoon boomers and buildups, at least you can get high enough to zig-zag around the big stuff and still have a nice ride in COOL air.

Flying in the summer SW in the afternoon (not in the mountains) you will be rocked by thermal turbulence below the mid-teens. I can fly Dallas to Vegas in the afternoons at 16-20 mostly without a bump.

Just today, flying KMEM (Memphis, TN) to KADS (Dallas, TX) it was solid IMC from 2K-14K until near the TX border. I was above it, in the clear, and smooth. Perfect day for flying if you go up there. Others on freq. weren't liking it much at all.

Part of it IMO is so many have a turbo and don't use it. Get an O2 Boom and go.

 

[wabower]

Whatever you gain on the down-wind leg will typically be paid back on the up-wind leg. When flying lower against the wind, the turbo'd plane is actually slower than its NA counterpart. BTDT.

It's a personal flying preference. Turbos will typically require you to fly at or above 8,000 ft to get a benefit in speed. If you fly low all the time, your benefit is increased maintenance cost.

However, if you can gain 10-15 kts by flying at 15,000 ft. vs. 6,000 ft and do so, then that means you're going, say 8-12% faster, then that reduces your cost per mile for the plane, which can offset the cost of the turbo. We've figured that on the 310, turbochargers would break even for us cost wise while allowing us to get the job done faster.

 

[Jthamilton]

What about those density altitudes here in Oklahoma when the summer temps are >100 creating a respectable density altitude.

I'm considering a 1979 turbo 182 rg. Nice thing about the aircraft is the turbo isn't required until your flying at 7,000 or so. This is going to allow my son and I to punch holes in the sky while enabling me to get above weather at times.

That being said if I didn't plan on flying to Colorado on a regular basis in would prob go with NA 182. My Cherokee 6 300 was pretty anemic on hot days with a few folks in back. Something I remember well.

Many think density altitude only affects folks in the mountains but you stop in the Midwest when it's hotter than hell your gonna feel the effects.

 

[CJones]

Whatever you gain on the down-wind leg will typically be paid back on the up-wind leg. When flying lower against the wind, the turbo'd plane is actually slower than its NA counterpart. BTDT.

Why is that? Temp restrictions on the turbo that limit power to below-NA power settings at lower altitudes?

 

[DouglasBader]

I've flown a lot of turbocharged and supercharged equipment, from T206's and T207's to T210's, 337's, 421's, PA31's, and various radial powered equipment that was turbocharged, supercharged, or both (or in the case of the R3350, turbo compound).

Very seldom have I used the boost capabilities of the aircraft much. Even when operating light singles in the mountains, I don't use much of the turbocharge capabilities, except to turbo normalize; I don't boost much above barometric, much of the time. If I do, it's not very high; 32" at most in many cases. I keep the temperatures down, and just don't need the extra boost. I seldom fly turbocharged airplanes at exceptionally high altitudes (exceptionally high for a light airplane, in my opinion, is above 12 or 13,000'. I don't even fly King Air's that high; they're not piston, but they don't like being much above 15,000 or 18,000. Turbocharged airplanes don't much care for it, either.

There's nothing wrong with having a turbocharged airplane if you're flying from a sea level location; airplanes climb higher, and you can certainly use the turbo as your barometric drops with altitude. I like to use turbos just enough to bring the power back up to a turbo normalized level, however, rather than boosting the engine to death, creating the potential for detonation, running high temps, and making the engine work any harder than it needs.

 

[ronnieh]

What Wayne said.
Doug, turbines don't like to be above 15,000 to 18,000 feet

 

[DouglasBader]

The turbine engine doesn't care, but the King Air 90's and 200's don't' do very well above those altitudes. They'll climb higher, but are real dogs at altitude.

Turboprop engines can be operated at much higher altitudes; I regularly operated the PT6A-66's on the Piaggio Avanti's at FL410. The BE20 tops out about FL270, but isn't really very happy much above FL180. The P180 gets the same fuel burn but nearly 400 KTAS at altitude. The difference is the airplane, not the power plant. A turboprop can be flown at high altitudes and do okay...but there are very few airframes that are conducive for it. Bigger turbo propeller aircraft are able to go higher; I flew the C-130 and while it's not a stellar performer much out of the 20's, it will get up there and cruise. Most turboprops are good teens and low twenty's aircraft.

Piston airplanes can be dragged high up, too, but the engines have to work hard to get them there, there's not that much cooling airflow in many cases, and it's rough on the equipment...and much of the equipment just doesn't have the wing for it.

If you get a chance to fly Navajos around and watch the cherry red turbo glowing through the louvers on the top of the engine, screaming away out there, you'll see how visibly hot that turbo is getting when the engine power is pushed up. I don't like to push it up that far.

When flying lower against the wind, the turbo'd plane is actually slower than its NA counterpart.

Aaaah...no.

Sounds like a nice "urban legend," though, much like getting on the "step" in cruise.

 

[wabower]

Most of the N/A vs. T/C numbers are bogus BS thrown around by pilots who have never taken time or effort to make accurate comparisons between similar airplanes. I'm currently looking at the POH for a 1964 N/A Cessna 210D and a 1981 T-210N.

Some takeoff comparisons:

At sea level, gross weight ground roll for the N/A 210 is 590'; to clear a 50; obstacle is 1,110' Increasing temp from 59F to 100F increases the roll to 850' and the obstruction clearance to 1,500'. Scary, ain't it?

The T-210 with the same cabin payload and fuel requires approximately 1,000' ground roll and 1,600' at sea level standard temp vs. 1,200' and 2,000' at 100C.

Bottom line is that N/A equivalent requires less roll and less obstacle clearance than its T/C counterpart on a hot Oklahoma day. Scary, ain't it?

Insofar as cruise altitudes and speed are concerned, those who contend that a turbo is necessary to get above the heat and bumps are wrong again. The N/A 210 will cruise at 15,000' at 150 KTAS, 50% power (16" X 2500 RPM) while the T-210 at 65% power will cruise at 163 KTAS.

For a trip with 400 nm cruise segment, the time difference between the two airplanes is less than 15 minutes. For the return trip against the wind at 5,000', TAS comparison and trip times are is a push.

What about those density altitudes here in Oklahoma when the summer temps are >100 creating a respectable density altitude.

I'm considering a 1979 turbo 182 rg. Nice thing about the aircraft is the turbo isn't required until your flying at 7,000 or so. This is going to allow my son and I to punch holes in the sky while enabling me to get above weather at times.

That being said if I didn't plan on flying to Colorado on a regular basis in would prob go with NA 182. My Cherokee 6 300 was pretty anemic on hot days with a few folks in back. Something I remember well.

Many think density altitude only affects folks in the mountains but you stop in the Midwest when it's hotter than hell your gonna feel the effects.

 

[Alexb2000]

I've flown a lot of turbocharged and supercharged equipment, from T206's and T207's to T210's, 337's, 421's, PA31's, and various radial powered equipment that was turbocharged, supercharged, or both (or in the case of the R3350, turbo compound).

Very seldom have I used the boost capabilities of the aircraft much. Even when operating light singles in the mountains, I don't use much of the turbocharge capabilities, except to turbo normalize; I don't boost much above barometric, much of the time. If I do, it's not very high; 32" at most in many cases. I keep the temperatures down, and just don't need the extra boost. I seldom fly turbocharged airplanes at exceptionally high altitudes (exceptionally high for a light airplane, in my opinion, is above 12 or 13,000'. I don't even fly King Air's that high; they're not piston, but they don't like being much above 15,000 or 18,000. Turbocharged airplanes don't much care for it, either.

There's nothing wrong with having a turbocharged airplane if you're flying from a sea level location; airplanes climb higher, and you can certainly use the turbo as your barometric drops with altitude. I like to use turbos just enough to bring the power back up to a turbo normalized level, however, rather than boosting the engine to death, creating the potential for detonation, running high temps, and making the engine work any harder than it needs.

If you only boost to barometric then you are in essence duplicating a turbo normalizer, except that you probably have a lower compression engine so less sea level HP than NA right?

I have a fair amount of time in a T206H. I can take off from any airport in the U.S. at gross and climb full power, Vy, to at least 25K without a temp issue of any kind. I can cruise anywhere in the teens or low 20's also without any kind of temp issues. Was this one aircraft or multiple examples you're referencing?

 

[ronnieh]

Doug I have spent many hours in a Chieften watching the red glow through the gill slits. On the ones I flew the EGT were close to the same at 8000 as 12,000. I would never exceed 1500 deg regardless. On the Chieften you did not use 43 inches for take off?

Your KA analogy is a little strange to me. I will admit the 90 is not much above 18,000. Same can be said for the MU2 (different engine) On the Cheyenne which is only slightly faster than the B200 at 15,000 feet I will be truing about 255 knots and burning around 700 pounds of fuel. At FL270 I am truing around 285 knots and burning around 580 pounds. Which is the best altitude? (assuming a suitable leg lenght)

 

[DouglasBader]

On the Chieften you did not use 43 inches for take off?

No.

Your KA analogy is a little strange to me. I will admit the 90 is not much above 18,000. Same can be said for the MU2 (different engine) On the Cheyenne which is only slightly faster than the B200 at 15,000 feet I will be truing about 255 knots and burning around 700 pounds of fuel. At FL270 I am truing around 285 knots and burning around 580 pounds. Which is the best altitude? (assuming a suitable leg lenght)

I was never very impressed with the Cheyenne, either.

If you only boost to barometric then you are in essence duplicating a turbo normalizer, except that you probably have a lower compression engine so less sea level HP than NA right?

Wrong. Same or greater sea level horsepower, and certainly capable of more horsepower (more torque, actually) at sea level, assuming one boosts the engine to it's limits. I simply choose not to, and the same in cruise; no need to boost the engine much, and seldom, if ever above about 32". No need.

I have a fair amount of time in a T206H. I can take off from any airport in the U.S. at gross and climb full power, Vy, to at least 25K without a temp issue of any kind. I can cruise anywhere in the teens or low 20's also without any kind of temp issues. Was this one aircraft or multiple examples you're referencing?

We had about thirty of them, primary 206's and 207's. A few were normally aspirated, and some weren't. Our operations were primarily at high density altitudes in mountainous terrain, and I often flew the normally aspirated airplanes out of those locations without much concern. I took care to go easy on the turbocharged airplanes, and seldom used much of the boosted capability, as it simply wasn't necessary.

The turbocharged airplanes weighed more, of course.

 

[wabower]

So on otherwise identical airplanes the extra weight of the turbo system is free?

Aaaah...no.

Sounds like a nice "urban legend," though, much like getting on the "step" in cruise.

 

[DouglasBader]

No, and it might make a difference if you were completely empty and working off minimum power, but it's not much of a difference, and that much difference can be found in varying fuel load or passenger weights. It's not much.

 

[ronnieh]

Doug, if you will look in the POH for the PA31-350, all take offs are at full throttle. The fuel servo is a "two hole design" that will not give proper fuel flow unless it as at full power. The auto waste gate should keep the MP at 43 inches on a standard day. I can imagine anybody taking a Chieften off at 30 inches or even 32 inches. Makes no sense to me. What ever works for you.

In the Cheyenne you say I should stay down at 15,000 and burn all the extra fuel at a much slower airspeed. The Cheyenne seems to fly very well in the upper 20's. Is there a light turbo prop (9 seats including pilot) that will true 290 knots+ at 26,000 feet that does impress you?

Must be some B200 or even straight 200 pilots on here. Do ya'll restrict your altitudes to 18,000?

Ted, or Henning one has some Navajo time. Do you use reduced power for TO in ther Navajo?

 

[wabower]

B-200 cruise speed is identical at 15,000 or FL 280. Only difference is that fuel burn drops by 34%, which would require a fuel stop from DFW to PHX. NFW.

Must be some B200 or even straight 200 pilots on here. Do ya'll restrict your altitudes to 18,000?

 

[ronnieh]

Wayne, I think you made my point. The speed numbers are not quite the same in the Cheyenne but close. I agree with the fuel burn.

So Wayne do you stay below 18,000 in the B200 on a 2 hour trip?

 

[wabower]

I did once, westbound to Detroit customs stop from Toronto fighting a 126-knot winter headwind on the nose that was less below FL200. Otherwise, hell no. Our 550 nm trip from Dallas to Destin was usually 2.0 +/- 5 min, normally flown at mid-high 20's, and as high as 330 (prior to RVSM) to top some bumpers.

Wayne, I think you made my point. The speed numbers are not quite the same in the Cheyenne but close. I agree with the fuel burn.

So Wayne do you stay below 18,000 in the B200 on a 2 hour trip?

 

[Ted]

Whatever you gain on the down-wind leg will typically be paid back on the up-wind leg. When flying lower against the wind, the turbo'd plane is actually slower than its NA counterpart. BTDT.

In the case of your 210 vs. T210, that was true. But as you know, the turbo options I'm considering are a bit more outside the box. Plus I think that the T210 didn't do a very good implementation of turbocharging - I would've designed the system differently. Then again, most factory turbo systems weren't much better.

Even still, if you fly long downwind legs as I tend to do, the speed benefits may still make sense. Right now I average 160 KTAS over the ground. Let's say that, flying at low altitude with turbos, my average goes to 150 KTAS on the downwind leg. That difference might be 30-45 minutes. On the downwind leg the next day, my typical 175 KTAS going up to about 200 KTAS will end up saving me about 90 minutes on the long day. Overall trip savings is still 45-60 minutes, and the ability to save an hour on the long day makes more sense to me.

When I bought the Aztec, I didn't want a turbocharged plane because I didn't want the extra maintenance and figured it wouldn't help me much. Of course, I also had no idea I was going to do stupid things like fly from LA to NYC in a day with it with 47 chihuahuas. But my missions are atypical, and I don't mind wearing funny O2 masks.

 

[Everskyward]

Wayne, I think you made my point. The speed numbers are not quite the same in the Cheyenne but close. I agree with the fuel burn.

So Wayne do you stay below 18,000 in the B200 on a 2 hour trip?

Not Wayne but we always flew the 200s around 21,000-22,000. Fuel burn was much less than at 18,000.

 

[wabower]

Some of your use clearly falls outside the norm for most airplanes, and is therefore ill-suited for the typical leg lengths flown by the fleet. Not many light twins fly Houston to Maine in one day--or several.

In the case of your 210 vs. T210, that was true. But as you know, the turbo options I'm considering are a bit more outside the box. Plus I think that the T210 didn't do a very good implementation of turbocharging - I would've designed the system differently. Then again, most factory turbo systems weren't much better.

Even still, if you fly long downwind legs as I tend to do, the speed benefits may still make sense. Right now I average 160 KTAS over the ground. Let's say that, flying at low altitude with turbos, my average goes to 150 KTAS on the downwind leg. That difference might be 30-45 minutes. On the downwind leg the next day, my typical 175 KTAS going up to about 200 KTAS will end up saving me about 90 minutes on the long day. Overall trip savings is still 45-60 minutes, and the ability to save an hour on the long day makes more sense to me.

When I bought the Aztec, I didn't want a turbocharged plane because I didn't want the extra maintenance and figured it wouldn't help me much. Of course, I also had no idea I was going to do stupid things like fly from LA to NYC in a day with it with 47 chihuahuas. But my missions are atypical, and I don't mind wearing funny O2 masks.

 

[Ted]

Ted, or Henning one has some Navajo time. Do you use reduced power for TO in ther Navajo?

Nope. Navajo takeoff is full throttle. The specific manifold pressure you get will vary depending on the day, as the engines have density controllers. The highest we've gotten is right at the 49" red line on a hot day in Denver last summer. Typically we see about 43-44". This is in the Chieftain.

We then reduce to 40"/2400 RPM for climb in the Chieftain, 35"/2400 RPM in the 310 HP Navajo.

 

[Ted]

Some of your use clearly falls outside the norm for any sane human, and is therefore ill-suited for the typical leg lengths flown by the fleet. Not many light twins fly Houston to Maine in one day--or several.

FTFY

And yes, my use is extremely atypical. Hence my caveat that it can make sense, but in the flatlands I believe that most people don't make good use of turbos.

So, we are in agreement.

 

[ronnieh]

Yep Ted, same numbers I got. If not real heavy I came back to 38" in the climb. Back in the day I ran 125 deg ROP (I know, I know, I said back in the day) never to exceed 1500 deg EGT in cruise and I tried to keep it down to 1400 in the climb. All the Chieftens I flew (all three of them) were prone to get the cylinders a little hot in the climb. I preferred 380 max but saw 400 from time to time.

 

[DouglasBader]

B-200 cruise speed is identical at 15,000 or FL 280. Only difference is that fuel burn drops by 34%,

That's not the only difference. Fuel burn decreases, but the airplane doesn't fly nearly as well at higher altitudes. Above about FL240, the airplane is a real dog, and flies with a steep enough angle of attack that in my opinion, it's not much good. The wing really struggles at altitude.

Most light turboprops are in their element in the teens to at best very low 20's. Above that, they're not much good.

Just because you can get there and stay there doesn't say much. It's a dog at altitude; they mostly all are.

 

[wabower]

I omitted the obvious conclusion regarding sanity, simply because I know the dogs are sooooo happy with the outcome.

FTFY

And yes, my use is extremely atypical. Hence my caveat that it can make sense, but in the flatlands I believe that most people don't make good use of turbos.

So, we are in agreement.

 

[Ted]

Yep Ted, same numbers I got. If not real heavy I came back to 38" in the climb. Back in the day I ran 125 deg ROP (I know, I know, I said back in the day) never to exceed 1500 deg EGT in cruise and I tried to keep it down to 1400 in the climb. All the Chieftens I flew (all three of them) were prone to get the cylinders a little hot in the climb. I preferred 380 max but saw 400 from time to time.

We don't have engine monitors, and we lean to a straight 1450 TIT.

I am trying to convince the owner of the Chieftain on purchasing an engine monitor and the benefits thereof (not to mention the fact that the thing will pay for itself in under 100 hours of flying). It may happen...

That's not the only difference. Fuel burn decreases, but the airplane doesn't fly nearly as well at higher altitudes. Above about FL240, the airplane is a real dog, and flies with a steep enough angle of attack that in my opinion, it's not much good. The wing really struggles at altitude.

Most light turboprops are in their element in the teens to at best very low 20's. Above that, they're not much good.

Just because you can get there and stay there doesn't say much. It's a dog at altitude; they mostly all are.

I'm not sure how this statement makes much sense, especially as it relates to turbine aircraft. They go high to get efficiency. You would prefer that they run down low and burn far more fuel? They're going to be on autopilot in cruise most of the time anyway.

It's not like on naturally aspirated piston aircraft, which are the closest comparison since turbines are naturally aspirated engines. I can fly low and the wing is happier or I can fly high and the wing is less happy. Fuel burn may go down a little when high, but not to the tune of 30+%.

I omitted the obvious conclusion regarding sanity, simply because I know the dogs are sooooo happy with the outcome.

The puppy kisses make it all worthwhile, always have.

Rethinking the idea I told you about a few weeks back in favor of a different one that should be easier to implement and be a bit faster.

 

[j1b3h0]

I don't mind flying a turbocharged airplane, but unless there was a real good reason for turbo vs NA, I wouldn't want to pay the additional freight. You know, you can build a 300hp 350 Chevy V8 and it will provide years and years of reliable service. I have a freind with an old (1994) Camaro with 380,000mi on his 305ci throttle body injected smallblock. Remarkable. You can Build a 350 Chevy that will develop 700hp! How long do you think that will last? People with such sort lifespans shouldn't buy any green bananas.

Same with airplane engines...a naturally aspirated 230hp IO-540 will last a long time between overhauls. A TIO-541 in a 380hp Beech Duke configuration not so much. Anyone who has spent some time in the high teens flying a Chieftain will tell, you yes the glowing red-hot exhaust system can be viewed through the louvers in the cowling (in fact it's hard to ignore). Engines can be made to produce sea level horsepower up to 17,000ft. But, you'll never achieve sea level cooling, because there is so little air, and the real problems occur during descent: You see, air-cooled engine cylinders are constructed of a steel sleeve bonded inside of aluminum alloy cooling fins, and the rate of expansion and - more importantly -contraction is different between the two (or more) metals, resulting in a strong propensity for cracks, very expensive. Obviously, pilots of turbo'd airplanes take measures...to let these highly heated engines cool off very slowly. They make shallow descents, (so as not to build up much speed) and when power reductions are necessary, they carefully plan and 'stage-cool'. A good method is to reduce 1" Manifold pressure per minute. Every time the second-hand sweeps 12, reduce 1". And the goal, of course, is to be completely done with the cooling just prior to glideslope intercept. Given the vagaries of ATC, this happens about as often as the mutual orgasm.

I would MUCH rather be in a turboprop...yeah, they're all dogs above the high teens, but they're mostly A) pressurized and B) mostly equipt with something other than a Sears Best intrument panel and C) while any ice is bad ice, a turboprop will probably schlep around enough ice for the happyhour, while the turbo'd piston will be seeking weather to divert. Also, if, for some reason I have to get on the ground fast, in a turbine airplane I can leave the flight levels like a set of car keys, and be on the ground in minutes...I can also slow down quickly. For instance, I used to regularly cross the San Mateo bridge at 250kts, and land on the numbers of San Fran's 28R. Never happen in a piston airplane. But hey, just one man's opinion.

 

[Ted]

Same with airplane engines...a naturally aspirated 230hp IO-540 will last a long time between overhauls. A TIO-541 in a 380hp Beech Duke configuration not so much.

The TIO-541 is a bad example of, well, everything.

Anyone who has spent some time in the high teens flying a Chieftain will tell, you yes the glowing red-hot exhaust system can be viewed through the louvers in the cowling (in fact it's hard to ignore).

Typically I only see them glowing at night - we don't let the TIT get that high.

Engines can be made to produce sea level horsepower up to 17,000ft. But, you'll never achieve sea level cooling, because there is so little air, and the real problems occur during descent: You see, air-cooled engine cylinders are constructed of a steel sleeve bonded inside of aluminum alloy cooling fins, and the rate of expansion and - more importantly -contraction is different between the two (or more) metals, resulting in a strong propensity for cracks, very expensive. Obviously, pilots of turbo'd airplanes take measures...to let these highly heated engines cool off very slowly. They make shallow descents, (so as not to build up much speed) and when power reductions are necessary, they carefully plan and 'stage-cool'. A good method is to reduce 1" Manifold pressure per minute. Every time the second-hand sweeps 12, reduce 1". And the goal, of course, is to be completely done with the cooling just prior to glideslope intercept. Given the vagaries of ATC, this happens about as often as the mutual orgasm.

Careful cooling is pretty simple to perform when planned. Yes, ATC can be a pain and if you're flying into and out of, say, the NY Bravo, but the rest of the time you can usually manipulate them well enough. Cooling is worse at higher altitudes, but more importantly the turbos are working harder. However, this can still be dealt with if the pilot is careful, and it works fine. The Chieftain isn't very good at altitude due to its lack of intercooler. However, other turbo engines (especially intercooled) work fine.

 

[wabower]

You wouldn't be in any of the turboprops around here for more than one trip if you started descending into ELP for gas on the way to PHX.

"Hey cap, why are we landing here? We've never needed a ELP fuel stop in the 10 years we've owned this plane. Are the winds that bad?"

"Nope, I just don't like the deck angle at 260 and much prefer 180 on the outbound. Fuel stop shouldn't take more than 30 minutes plus taxi time, takeoff, climb, etc. Total trip time shouldn't be much over four hours."

"Four hours? YGBSM. We usually make it non-stop in three. Anybody got Wayne's cell on speed dial? Call and ask if he wants to come out and play golf in Scottsdale for a few days and fly the plane home. Tell him the dude we hired just stopped in El Paso because he doesn't like to fly high, so he won't be with us after today."

I would MUCH rather be in a turboprop...yeah, they're all dogs above the high teens, but they're mostly A) pressurized and B) mostly equipt with something other than a Sears Best intrument panel and C) while any ice is bad ice, a turboprop will probably schlep around enough ice for the happyhour, while the turbo'd piston will be seeking weather to divert. .

 

[kgruber]

Typically I only see them glowing at night - we don't let the TIT get that high.

No they don't. Must be poor maintenance. Or too much WD-40.

 

[j1b3h0]

Naturally aspirated is fine for flatlanders, 95% of the time. Most flatlanders with turbos fly at 10,000ft or less unless they have a good reason to go higher - good enough to don an oxygen mask, because of really bad weather, for example (speaks to poor flight planning). Just not worth it, IMO. I'm guessing, but 4 times the cost?

 

[j1b3h0]

No they don't. Must be poor maintenance. Or too much WD-40.

They all glow at night. Maint was excellent on the airplanes I flew for the largest 135 operator in the US and the largest operator of Navajos in the world. Worked for them in '83-84. They're still in business. Piper calls them for Navajo advice.

 

[DouglasBader]

Poor maintenance doesn't make turbos glow. Temperatures do, and the P Navajo's turbos glow at night. One doesn't usually see them in the daytime.

I'm not sure how this statement makes much sense, especially as it relates to turbine aircraft. They go high to get efficiency. You would prefer that they run down low and burn far more fuel? They're going to be on autopilot in cruise most of the time anyway.

Cruise altitude in a turbine airplane isn't simply a matter of flying high for efficiency. There is an optimum altitude for a given weight and power; above that is less efficient, and below that is left efficient. It's far more than simply being high enough.

Most turbine engines operate at their most efficient point about 90% of the core speed, whether that's an N2 speed or Ng speed. Operating at lower speeds is typically less efficient, and operating above those speeds is less efficient.

At lower altitudes where less power is required to hold a given flight condition AoA, cruise or climb airspeed, rate of climb, etc, a lower engine speed is required. At the optimum altitude, the engine is operating at higher settings and closer to it's optimum speed. The principles behind this vary with the type of engine (including the type of turboprop; the operation of a garret/honeywell vs. a Pratt, for example, is different), but the principle remains the same. For engine operation, the optimum altitude is the altitude for a given weight (and outside air temperature) that allows the engine to operate in it's most efficient range for a given desired condition.

It's not at all a matter of simply climbing higher and higher.

When westbound, one looks at the winds aloft and selects an altitude based on engine/cruise efficiency as well as the winds. Higher isn't always better. Same eastbound, but one looks for the most efficient winds, as well.

In the 250 knot range at FL270 (give or take), you're little more than a flying roadblock to the national airspace system.

 

[wabower]

How do you define efficiency and who cares? The GIB wants to be there now, he bought the airplane to go fast and that's what he expects the crew to provide. The only time you're allowed go slower than as fast as you can is when a fuel stop would be required, in which case you can pull it back until the FMS shows 600# over destination.

Cruise altitude in a turbine airplane isn't simply a matter of flying high for efficiency. There is an optimum altitude for a given weight and power; above that is less efficient, and below that is left efficient. It's far more than simply being high enough.

Most turbine engines operate at their most efficient point about 90% of the core speed, whether that's an N2 speed or Ng speed. Operating at lower speeds is typically less efficient, and operating above those speeds is less efficient.

At lower altitudes where less power is required to hold a given flight condition AoA, cruise or climb airspeed, rate of climb, etc, a lower engine speed is required. At the optimum altitude, the engine is operating at higher settings and closer to it's optimum speed. The principles behind this vary with the type of engine (including the type of turboprop; the operation of a garret/honeywell vs. a Pratt, for example, is different), but the principle remains the same. For engine operation, the optimum altitude is the altitude for a given weight (and outside air temperature) that allows the engine to operate in it's most efficient range for a given desired condition.

It's not at all a matter of simply climbing higher and higher.

When westbound, one looks at the winds aloft and selects an altitude based on engine/cruise efficiency as well as the winds. Higher isn't always better. Same eastbound, but one looks for the most efficient winds, as well.

In the 250 knot range at FL270 (give or take), you're little more than a flying roadblock to the national airspace system.

 

[ronnieh]

Wayne, best just let it go. Doug can stay down at 16,000. He won't get vectored around too awful much. He is only going to get about 30% less fuel milage. The gas milage is not that big of a deal. Kerosene is still under 6 bucks in a lot of places. An extra hour for a fuel stop as you pointed out, no biggie. After all it is not like the owner is in any particular hurry.

Me, I am leaving for SEP in the morning. A little more than 2 hours and I will be at or above FL260, hanging on the props with close to a 10 deg nose up attitude, being a road block (not).

 

[DouglasBader]

How do you define efficiency and who cares?

Performance engineers. Aircraft manufacturers. Aeronautical engineers.

We fly turbine aircraft based on the most efficient operation, you see. Have you never heard of a cost index?

 

[wabower]

I have never seen a cost index. What is it? If it were truly important, wouldn't somebody have mentioned it by now? When would an airplane owner ever need it, and for what? We bought the plane to perform a specific job at specific speed. We know the planes that are capable of performing the mission. Why in the world do we need a cost index?. How would it matter to me when flying non-stop in my B-200 to Phoenix or Jackson Hole?

Performance engineers. Aircraft manufacturers. Aeronautical engineers.

We fly turbine aircraft based on the most efficient operation, you see. Have you never heard of a cost index?