New small turbines, 200hp in the works

[Doc Holliday]

Really? Most turbine helicopters I've run usually have a max TOT limit prior to start due to the drive train load. But every RFM states to perform a dry motor to get the TOT down to an acceptable level (usually 150). Then you initiate the start. During certain ground mx procedures like T/R balance I might do 5 or 6 runs in the span of 20 minutes. Don't recall a similar start temp limit on the King Airs or other fixed wing aircraft I've run before, only a max limit. Does your aircraft have such a limit?

Same here. While an engine may have a start temp limit there's no reason to just motor the engine through and bring the temp down.

I once went out on a flight in a 500C with an owner. He told me we would have to wait because the TOT was at 200, and we needed 150. I explained to him the concept of motoring to bring the temp down, then showed him. Pushed the start button, motored and when it got to 150 introduced fuel, normal start.

And that start actually only was a few seconds longer than a normal cold start.

 

[Velocity173]

60 secs on
60 secs off
60 secs on
60 secs off
60 secs on
30 mins off

150 MGT or below RECOMMENDED for cooler starts / hot start. If it’s slightly above I generally don’t worry about motoring to get below 150. FADEC will save her anyway.

 

[Tarheelpilot]

60 secs on
60 secs off
60 secs on
60 secs off
60 secs on

30 mins off

150 MGT or below RECOMMENDED for cooler starts / hot start. If it’s slightly above I generally don’t worry about motoring to get below 150. FADEC will save her anyway.

the fadec on my ride will auto abort the start if fuel is introduced above the temp limit.

 

[Ted]

Traditional turbines are not efficient until you get pretty high. Don't see this being worth it compared to pistons.

Keep in mind a lot of that had to do with older designs that had low pressure ratios and fairly mundane materials that keep a "low" maximum EGT. Turbines do inherently get more efficient as they get larger (just look at the GE90 as an example), but there hasn't been enough money to make it worth making a more efficient smaller turbine. Mostly just more power - hence why you see @flyingcheesehead report that the ground idle in the TBM is the same as ground idle for BOTH engines in the MU-2. Really the TBM isn't much more efficient than an MU-2.

TBH, I don't "fiddle" much. Once in and out for prime, in after start, lean for roughly constant EGT during climb, lean to just LOP for cruise, rich for landing.

In a way, the leaning during climb is analogous to fiddling with the power lever during climb... It's just that the climb is much shorter so usually I'll only have to pull the mixture back 2-3 times during the climb. I'm constantly fiddling with the power lever during climb to get at least 95%/115% torque, depending if I'm flying the 850 or 900.

Yeah, but you're used to flying pistons. Think about the number of people that don't understand how to use a mixture knob, don't have proper instrumentation, and/or don't understand their fuel system. So they leave it in full rich for climb or they use the "% power" numbers that some fuel flow gauges have on them (like Twin Cessnas).

Turbine? Simple. There's a redline. Adjust to stay below it. The -1s I fly on the MU-2 have a variable EGT so that adds a bit of complexity, but when the OAT gauge points to the OAT it has an overlay that also shows what your redline is for that temperature.

I'm starting to think maybe it's the fact that I'm flying two different planes with somewhat different procedures...

In the 850, there's three power levers and a rocker switch for the starter. Ignition Auto, Boost pump on, starter switch on, check for rotation and oil pressure, at 13%Ng put the condition lever in lo idle, make sure it lights up, make sure it hits 30%Ng in less than 30 seconds, secondaries come on at about 40%, turn the starter switch back off at 50%, condition lever to hi idle at 53%, Ng stabilizes at 69±2%, we have a good start...

It's kinda similar in the 900 except the starter switch is a momentary switch that you hold for two seconds, and the starter will cut itself off automatically at 50%, though you do have to monitor it to make sure it does so. You also don't have a condition lever (or a prop lever), the power lever is like three legs of a stick shift (with "3rd gear" missing). Essentially, the right-hand leg of the h is the condition lever, the center shelf of the h is the prop, the top left is the normal power range and the bottom left is beta/reverse.

That makes things more confusing and is probably a lot of it for you. It's sort of that idea of having a private pilot go between a Cherokee and a 172 during the early hours of training. Both are simple to fly, but they have slight differences. Once you get the hang of things then it's easy to go back and forth.

Similarly, if you fly PT-6s and TPE-331s, there are some differences that take some getting used to, and if you're not solid on your turbine procedures on one engine, the other probably will seem somewhat confusing. Sort of like starting and some of the nuances of Lycomings vs. Continentals. They both are basically the same but there are some differences.

Well, generally I leave the Mooney plugged in below 40F... Cold starts are normal, hot starts use your procedure, and the only other thing that varies with temp is how long I prime.

OTOH, in the TBM it's not uncommon for us to be doing a quick-ish turn. An actual quick turn, we really can't do without a GPU, especially in the 850, and many FBOs refuse to give you the GPU on a TBM because they put the power port up at the engine compartment, so the lineman has to get within an arm's length of a spinning prop to unplug it. (I don't like that much either, for that matter.)

Generally, we'll open up the covers and wait for the ITT to come down to about 260C before attempting a start, and we'll wait until it's been spinning for 20 seconds to light it up. We need to have about 20-30 minutes between shutdown and restart, though... And I don't have to worry about that at all in the Mooney, I can shut down and start right back up again if I want/need to.

I'm not a TBM expert and obviously you're governed by the rules of the operation you fly for. However that doesn't make any sense to me, as some others have said. If you can't do a battery start when hot on that plane then it sounds like you have a battery issue. As noted, you can motor the engine to get the EGT/ITT down to the acceptable pre-start level. I have quick-turns on the MU-2 and it's never been an issue, and unlike pistons (where even I sometimes have had unusual hot start issues on quick turns), never a problem with a turbine.

It sounds to me like there's room for some procedure changes there.

I've probably got most of that - It just seems like a lot to pay attention to. Or maybe it's just that I'm even more wary because it's a lot easier to cook an engine on the start, and it costs 10x what mine does.

That's part of what you get used to in that first 100 starts. Just about everyone who starts flying turbines coming from pistons (except maybe on the airlines) is initially terrified of roasting an engine in a hot start. But the reality is it's very rare to have one, and once you have your scan up you know what a good start looks like vs. a bad one.

There's a calendar time aspect too, since cold OATs in the winter, high altitude conditions, and hot OATs in the summer will also make starts slightly different.

Don't worry, you'll get the hang of it. And ultimately it is simpler, you just have to get used to the differences.

 

[Kenny Phillips]

If they can ever perfect unlimited life ceramic turbine wheels, there won't be a recip left in the air or on the ground.

Well, 'cuz my day job is in that business, you'd need to perfect ceramic turbines and stators that were cheap and easy to manufacture. Pressures and temperatures would need to go waaaaaaaay up to increase efficiency. Fifty grand retail would be a magic number. $100K, much smaller market. But even $150K is a pipe dream, as it would likely cost in excess of five hundred million to certify, given the new materials.

 

[flyingcheesehead]

Actually not really on the purpose-built side. You just need to select the right aircraft for a turbine upgrade. There have been many over the years just like the Soloy conversions above. Case in point:
http://www.zenithair.com/misc/turbine-power.html

I got myself thinking "Jet" as opposed to just "Turbine". Yeah, a turboprop RV could work... I was just thinking about the BD-5J and trying to think of how you'd mount a jet in an RV. Clearly there was too much blood in my coffee stream at the time.

In 15,000+ hours of flying turbines I've never seen a hot start. Had a few hung starts, a few no light off starts, but never a hot start.

I understand that they're very rare... That's why the YouTube video of a hot start is kinda funny. The instructor just gets finished saying "You watch this temp here for a hot start, but that never happe... oops!" as he quickly shuts it down.

Why?

Really? Most turbine helicopters I've run usually have a max TOT limit prior to start due to the drive train load. But every RFM states to perform a dry motor to get the TOT down to an acceptable level (usually 150). Then you initiate the start. During certain ground mx procedures like T/R balance I might do 5 or 6 runs in the span of 20 minutes. Don't recall a similar start temp limit on the King Airs or other fixed wing aircraft I've run before, only a max limit. Does your aircraft have such a limit?

It's a limit on the starter. We get:

1 minute on, 1 minute off
1 minute on, 5 minutes off
1 minute on, 30 minutes off.

If we're going to actually start the engine, we need to light it up by 20 seconds to have a successful start within a minute. If the 20 seconds doesn't get the temp down far enough and we have to motor it and wait a minute, I'm told the ITT comes back up almost to where it was. Fail again, and you sit and wait, which makes pax unhappy. Fail again, and you might as well have waited for it to just cool down on its own.

One thing I'm going to be working on is looking at data for quick turns to come up with some better guidelines as to when it's OK to start. I think we're a bit on the conservative side.

Yeah, but you're used to flying pistons. Think about the number of people that don't understand how to use a mixture knob, don't have proper instrumentation, and/or don't understand their fuel system. So they leave it in full rich for climb or they use the "% power" numbers that some fuel flow gauges have on them (like Twin Cessnas).

Turbine? Simple. There's a redline. Adjust to stay below it. The -1s I fly on the MU-2 have a variable EGT so that adds a bit of complexity, but when the OAT gauge points to the OAT it has an overlay that also shows what your redline is for that temperature.

Yeah, I guess piston engine management is such a no-brainer to me now, and the turbines new enough, that pistons just seem easier. Let's revisit the subject in a few more years.

 

[flyingcheesehead]

Actually not really on the purpose-built side. You just need to select the right aircraft for a turbine upgrade. There have been many over the years just like the Soloy conversions above. Case in point:
http://www.zenithair.com/misc/turbine-power.html

I got myself thinking "Jet" as opposed to just "Turbine". Yeah, a turboprop RV could work... I was just thinking about the BD-5J and trying to think of how you'd mount a jet in an RV. Clearly there was too much blood in my coffee stream at the time.

In 15,000+ hours of flying turbines I've never seen a hot start. Had a few hung starts, a few no light off starts, but never a hot start.

I understand that they're very rare... That's why the YouTube video of a hot start is kinda funny. The instructor just gets finished saying "You watch this temp here for a hot start, but that never happe... oops!" as he quickly shuts it down.

Why?

Really? Most turbine helicopters I've run usually have a max TOT limit prior to start due to the drive train load. But every RFM states to perform a dry motor to get the TOT down to an acceptable level (usually 150). Then you initiate the start. During certain ground mx procedures like T/R balance I might do 5 or 6 runs in the span of 20 minutes. Don't recall a similar start temp limit on the King Airs or other fixed wing aircraft I've run before, only a max limit. Does your aircraft have such a limit?

It's a limit on the starter. We get:

1 minute on, 1 minute off
1 minute on, 5 minutes off
1 minute on, 30 minutes off.

If we're going to actually start the engine, we need to light it up by 20 seconds to have a successful start within a minute. If the 20 seconds doesn't get the temp down far enough and we have to motor it and wait a minute, I'm told the ITT comes back up almost to where it was. Fail again, and you sit and wait, which makes pax unhappy. Fail again, and you might as well have waited for it to just cool down on its own.

One thing I'm going to be working on is looking at data for quick turns to come up with some better guidelines as to when it's OK to start. I think we're a bit on the conservative side.

Yeah, but you're used to flying pistons. Think about the number of people that don't understand how to use a mixture knob, don't have proper instrumentation, and/or don't understand their fuel system. So they leave it in full rich for climb or they use the "% power" numbers that some fuel flow gauges have on them (like Twin Cessnas).

Turbine? Simple. There's a redline. Adjust to stay below it. The -1s I fly on the MU-2 have a variable EGT so that adds a bit of complexity, but when the OAT gauge points to the OAT it has an overlay that also shows what your redline is for that temperature.

Yeah, I guess piston engine management is such a no-brainer to me now, and the turbines new enough, that pistons just seem easier. Let's revisit the subject in a few more years.

 

[Doc Holliday]

It's a limit on the starter. We get:

1 minute on, 1 minute off
1 minute on, 5 minutes off
1 minute on, 30 minutes off.

If we're going to actually start the engine, we need to light it up by 20 seconds to have a successful start within a minute. If the 20 seconds doesn't get the temp down far enough and we have to motor it and wait a minute, I'm told the ITT comes back up almost to where it was. Fail again, and you sit and wait, which makes pax unhappy. Fail again, and you might as well have waited for it to just cool down on its own.

One thing I'm going to be working on is looking at data for quick turns to come up with some better guidelines as to when it's OK to start. I think we're a bit on the conservative side.

I looked at an TBM-850 manual last night and could not find a limit on ITT (temp) for starting. Like previously mentioned, Allison sets it at 150C, but the PT-6-66 in the TBM doesn't mention a number.

Most turbine start cycles are under 45 seconds, so I can't imagine why a starter limit (1 minute) would be of concern. And I haven't seen a ITT or TOT rise back to the static temp after a 1 minute motoring.

Is this stuff the training center is teaching? I have to ask, because I've seen and heard some pretty ridiculous claims made by FS and SimCom in the programs.

 

[flyingcheesehead]

I looked at an TBM-850 manual last night and could not find a limit on ITT (temp) for starting.

There isn't one for before start. During start it's 1000ºC for 5 seconds, 870ºC for 20 seconds, or 850ºC otherwise. Normal operating max is 840ºC. (I looked, it is there on page 2.3.1 of the POH. Starter limits are on 2.4.1.)

However, we don't go beyond the 850 number, period. It may be allowed, but supposedly it's very bad for the wallet when it's time for a hot section.

Also, the 1 minute operating limit for the starter isn't the whole story. It's only 30 seconds below 30%Ng ("30 in 30" is one of our call-outs on the start). So, you can only motor it for 30 seconds. Like I previously mentioned, if you don't light it up by 20 seconds, you won't make it to 30% by 30 seconds.

Like previously mentioned, Allison sets it at 150C, but the PT-6-66 in the TBM doesn't mention a number.

Sounds like you meant a before-start number. There isn't one... You just have limits to obey *during* the start. We operate a little on the conservative side to avoid that.

Most turbine start cycles are under 45 seconds, so I can't imagine why a starter limit (1 minute) would be of concern. And I haven't seen a ITT or TOT rise back to the static temp after a 1 minute motoring.

It's about the wait required before further attempts. There's no concern about the 1 minute limit on operation.

Is this stuff the training center is teaching? I have to ask, because I've seen and heard some pretty ridiculous claims made by FS and SimCom in the programs.

No, just how we operate.

One thing the SimCom instructor did say that you reminded me of is that on start, if you're exceeding 870ºC for the 5 seconds it's allowed to go up to 1000ºC, that you shouldn't be counting "one one thousand, two one thousand" etc. but instead "$one hundred thousand, $two hundred thousand..."

Also, FWIW SimCom's checklists suggest motoring above 150ºC, but going from motoring to a start (20 seconds turning before lighting the fire) works fine up to probably 300ºC ITT, maybe even 350ºC if the conditions are right (cold OAT, headwind, etc).

One of the most noticeable differences between the 850 and the 900 is that the redesigned air inlet helps engine cooling a LOT. It allows us to keep higher power settings in the upper altitudes as well. It's a large part of why the 900 is faster.

 

[Doc Holliday]

There isn't one for before start. During start it's 1000ºC for 5 seconds, 870ºC for 20 seconds, or 850ºC otherwise. Normal operating max is 840ºC. (I looked, it is there on page 2.3.1 of the POH. Starter limits are on 2.4.1.)

However, we don't go beyond the 850 number, period. It may be allowed, but supposedly it's very bad for the wallet when it's time for a hot section.

Also, the 1 minute operating limit for the starter isn't the whole story. It's only 30 seconds below 30%Ng ("30 in 30" is one of our call-outs on the start). So, you can only motor it for 30 seconds. Like I previously mentioned, if you don't light it up by 20 seconds, you won't make it to 30% by 30 seconds.



Sounds like you meant a before-start number. There isn't one... You just have limits to obey *during* the start. We operate a little on the conservative side to avoid that.



It's about the wait required before further attempts. There's no concern about the 1 minute limit on operation.



No, just how we operate.

One thing the SimCom instructor did say that you reminded me of is that on start, if you're exceeding 870ºC for the 5 seconds it's allowed to go up to 1000ºC, that you shouldn't be counting "one one thousand, two one thousand" etc. but instead "$one hundred thousand, $two hundred thousand..."

Also, FWIW SimCom's checklists suggest motoring above 150ºC, but going from motoring to a start (20 seconds turning before lighting the fire) works fine up to probably 300ºC ITT, maybe even 350ºC if the conditions are right (cold OAT, headwind, etc).

One of the most noticeable differences between the 850 and the 900 is that the redesigned air inlet helps engine cooling a LOT. It allows us to keep higher power settings in the upper altitudes as well. It's a large part of why the 900 is faster.

OK, so I still don't get this:

Generally, we'll open up the covers and wait for the ITT to come down to about 260C before attempting a start, and we'll wait until it's been spinning for 20 seconds to light it up. We need to have about 20-30 minutes between shutdown and restart, though... And I don't have to worry about that at all in the Mooney, I can shut down and start right back up again if I want/need to.

Looks like a self imposed restriction. So in reality there's nothing preventing a shutdown and restart within just a few minutes.

 

[James_Dean]

On the Conquest, I motor until I'm below 100°C and then light it off. It only takes a few extra seconds vs. a cold start, but certainly decreases the top temp. I've only done about 1000 starts on PT-6's, but have yet to see one go past continuous cruise ITT limit even on a very short turn.

 

[Ted]

On the Conquest, I motor until I'm below 100°C and then light it off. It only takes a few extra seconds vs. a cold start, but certainly decreases the top temp. I've only done about 1000 starts on PT-6's, but have yet to see one go past continuous cruise ITT limit even on a very short turn.

PT-6s are notoriously cold during start. I've only had a couple hundred PT-6 starts, the only one I've seen above the normal operating limit during start was on a 1900D (I think that's -67s), and the pilots said it was a tired engine.

Kent, I think your operation is self-limiting due to being overly conservative. That's perfectly fine, but you can't blame the machine for operational decisions. And as the new guy, you probably also shouldn't waltz in and say "Well these guys on the internet said we're being too conservative..."

 

[James_Dean]

Kent,

I'd be concerned that the motor, wait, motor is killing your battery life and making a trend to hotter starts more likely. IOW, seems a little self defeating to me, and probably causes more frequent battery replacement. These batteries are generally damn expensive, but I have absolutely no TBM experience.

 

[Bell206]

killing your battery life

Battery charge/health is everything on turbine starts. Even with NiCads once you lose that 1st start and depending on battery condition that 2nd one starts you down that slippery slope. A number of years ago there was an uptick in hot starts in our Bell 206/407 fleet. After digging into it they found the average age of the NiCads in service was over 12 years. Did a fleet change to new NiCads and the hot start trend disappeared.

 

[Velocity173]

Battery we use. Chump change.

https://www.aircraftspruce.com/catalog/elpages/gill7407-28.php

 

[Bell206]

Battery we use.

All the old day job EMS aircraft went lead acid but the offshore side stayed NiCad due to the daily start load.

 

[flyingcheesehead]

Looks like a self imposed restriction. So in reality there's nothing preventing a shutdown and restart within just a few minutes.

Like I said, we do operate on the conservative side.

On the Conquest, I motor until I'm below 100°C and then light it off. It only takes a few extra seconds vs. a cold start, but certainly decreases the top temp. I've only done about 1000 starts on PT-6's, but have yet to see one go past continuous cruise ITT limit even on a very short turn.

The particular installation does matter. The 900's redesigned air intake makes it way better at quick turns than the 850.

Kent, I think your operation is self-limiting due to being overly conservative. That's perfectly fine, but you can't blame the machine for operational decisions. And as the new guy, you probably also shouldn't waltz in and say "Well these guys on the internet said we're being too conservative..."

Yes, we are, as I've stated. We'll change at some point - AFTER I have hard data in hand to come up with guidelines for when it's OK to start based on ITT, OAT, winds, etc.

Kent,

I'd be concerned that the motor, wait, motor is killing your battery life and making a trend to hotter starts more likely. IOW, seems a little self defeating to me, and probably causes more frequent battery replacement. These batteries are generally damn expensive, but I have absolutely no TBM experience.

That's why we don't do it - We just wait for the engine to cool down to the point where we can motor for 20 seconds and then light it up. And yes, those are $5,000 batteries.

 

[Velocity173]

Interesting use of a turbine. Never knew this car even existed.

 

[EppyGA]

How about this one?

 

[Bell206]

Never knew this car even existed.

https://en.wikipedia.org/wiki/Category:Cars_powered_by_gas_turbines

 

[flyingcheesehead]

Interesting use of a turbine. Never knew this car even existed.

I was kinda aware that it had, but it's really cool to see it actually running like that. Reminds me of an EV in a lot of ways, too!

 

[Velocity173]

I was kinda aware that it had, but it's really cool to see it actually running like that. Reminds me of an EV in a lot of ways, too!

Yeah, I was aware of auto racing / prototype applications of turbines, just never seen one designed for a daily driver. Especially one designed back in 1963.

It reminds of the EV-1 from GM. Make some for a test crowd to lease and see what bites. Then suddenly pull them off the market and destroy almost all of them. Of course the EV-1 was pulled for different reasons though.

 

[Ted]

Interesting use of a turbine. Never knew this car even existed.

Jay has a couple of turbine powered vehicles, including a motorcycle and another one that he built that looks like a Cadillac (because it was designed by GM and, well, GM designs Cadillacs). Those were more one-offs, though.

I think with the advent of turbines it made sense to try. However between idle fuel burn and the time to start there's no way to make them viable replacements for piston engines. Too bad, though, because if they did that then the experimental (and perhaps certified) aircraft world would have a source for inexpensive turbines.

It reminds of the EV-1 from GM. Make some for a test crowd to lease and see what bites. Then suddenly pull them off the market and destroy almost all of them. Of course the EV-1 was pulled for different reasons though.

I remember seeing the EV-1 at the GM building when it came out and wondered what happened to it. Like most first iterations of a not yet mature technology, I suppose it didn't do too great. GM did do some interesting things in the 90s, though.

 

[flyingcheesehead]

I remember seeing the EV-1 at the GM building when it came out and wondered what happened to it. Like most first iterations of a not yet mature technology, I suppose it didn't do too great. GM did do some interesting things in the 90s, though.

The people who had EV-1s loved them, and begged to be able to keep them. But, it was a vehicle GM made as an attempt to get in line with future CARB rules, and lawsuits from the auto manufacturers got those rules changed to where they no longer had to do EVs (at the time) so GM decided to kill 'em off.

They first had Lead-acid batteries and a range of 60 miles, later replaced with NiMH batteries which gave them a 160-mile range. The rights to use NiMH in vehicles were tied up because the patents were owned by ChevronTexaco until they expired in late 2018. The only reason EVs are where they are today is because Li-Ion batteries became viable.

 

[flyer770]

I see your turbine car and raise you to a turbine locomotive.