King Air C-90

[wabower]

I assumed the information might be airplane-specific to Cheyennes. No problemo, noboby has a monopoly on brain cramps.:wink2:

The trick-start procedure for the King Air (if the normal method doesn't work) is to try using motor only plus autofeather to see if the ignition circuit will fire. Rather than go through that monkey-motion I would probably just ask the shop to check the igniter box, they are somewhat failure-prone.

Wayne, I can only plead the time of night I posted that caused a few brain cells to mis fire. I was at Sim Com in Orlando for initial CHEYENNE IIIA school. They start the school with that picture which is the first time I had heard the term CEM. Everything in that particular posts was concerning a IIIA. No more late night posts for me.
BTW it is 10% on the -61
There is an auto ignite-off-manual ignite on the IIIA
The auto position allows ignition when condition levers are out of off and torque below 400 pounds.
Anyway, my bad, Cheyenne not KA. Thanks for pointing that out, we do not need more confusion on the turbines.

 

[Everskyward]

Well, the PT-6 is told to me here to not be able to feed fuel below a safe N2. That means the only way you should be able to hot start is with a significant enough tail wind up the pipe, and that is incompetence. Oh yes, I understand that there are greater risks. However... I don't know any other that is uninsurable and that says a lot.

I didn't realize we were only talking about the PT-6. Wayne has pointed out some ways in which they are not foolproof. As far as other turbine engines go, there are some that are not even close to foolproof.

 

[Dave Siciliano]

Just climb higher until you temp out rather than torque out.

Thanks. I'm on that track and with summer near, that should come lower. The pressure differential in the cabin comes into play at some point too. I don't like being over 8,000 inside on long trips. It's 7,000 at Fl200.

Dave

 

[gismo]

I don't think anybody ever waits long enough to determine if the problem will heal itself.

Maybe if the pilot was a Las Vegas high roller.

 

[gismo]

According to Wayne, as long as the systems are working correctly if it doesn't make 12% N2. A low battery will end up in a hung start with the fuel controller never feeding fuel if I understand him correctly.

AFaIK, you can still get a hung start after fuel is introduced and I expect that would likely deteriorate to a hot start if you didn't cut the fuel off.

This video of a hot start doesn't show much but is still interesting to watch, especially the first and last comment ("that never happens", and "that was interesting").
http://www.pacificnorthwestflying.com/index.php?topic=6718.0

 

[ronnieh]

Wayne needs to wade in on this but, I think the hung start is due to the secondary fuel nozzles not providing fuel. In other words the fuel divider only lets the first set come in and then at some N1 above starting N1 the additional fuel is added to bring the RPM up to a stabil idle. If the additional fuel does not flow it will hang up at whatever the max RPM available on the "start" fuel is. Typically maybe it will accelerate to maybe 20-30% and just set there. I don't know what the ITT will do. The low battery will simply not let the starter motor help the acceleration and can result in not enough air for the fuel being introduced resulting in a hot start. A hot start may continue into a normal start but simply exceed the max temps allowed. At that point the damage may be done already.
A hot start does not always mean a catastrophic failure right then. It depends on how severe, it may just show up as premature failure later. Perhaps a more expensive HSI.
Dave I would guess you will be temp limited well before FL200 in winter or summer. I am not familiar with the -21 but would just GUESS on a standard day by 15,000, perhaps lower.

 

[denverpilot]

This video of a hot start doesn't show much but is still interesting to watch, especially the first and last comment ("that never happens", and "that was interesting").
http://www.pacificnorthwestflying.com/index.php?topic=6718.0

The description on YT says this hot start was due to the "isolate switch". Anyone care to explain what that is? Google reveals nothing.

I get the distinct impression the condition lever is already forward (and shouldn't be? - honest question) because of the right seater's comment to "pull it back" if the temp goes too high. He never mentions waiting for N1 to stabilize prior to putting it forward.

I also get a sense of "this feels rushed" from the video too. And complacency. The words "that never happens" coming from the right seater seem to me to be a big red flag to slow down and ask a couple of questions. Why not? If it never happens, why are we watching for it? And how fast does it happen and will I need to react?

The video poster says he talked with the owner and there was no damage to the engine. Could have been expensive.

I also wonder if the video was a CEM for the right seat demo guy? Grounding the aircraft during a sales demo probably didn't lead to a sale.

 

[Dave Siciliano]

Dave I would guess you will be temp limited well before FL200 in winter or summer. I am not familiar with the -21 but would just GUESS on a standard day by 15,000, perhaps lower.

Yes, I was actually mixing two different thoughts: one was temps and the other was decent fuel economy. I filed for FL210 tomorrow and I'll do the power readings there from the POH and from Tom's recommended power settings for the C90-1. May try 230 too just to see the difference. I'll set it up to book criteria so I can see where I am compared to book numbers.

I tested the flow packs already and they seem fine up to 11 or 12,000. Hard to do higher on a trip with any passengers and I have a nice fellow multi pilot with me tomorrow.

Thanks,

Dave

 

[Dave Siciliano]

Each of these planes and different engines can have different switches and methods of starting. I have no idea what the 'isolate' switch might be other than on the intercom (g).

Best,

Dave

 

[kgruber]

The Sundstrand King Air at Paine Field had a pretty big engine fire, kind of hot start related.

They were doing a compressor wash with (What is the name of that stuff, Jettrol, Jantrol, or something flammable)....found it, Turco.

Anyway, the pilot was supposed to motor the engine, but had the switch in the start position. The ignitors touched it off and the engine burned pretty good. I can't recall the outcome, other than the pilot somehow didn't lose his job.

 

[wabower]

ronnieh;883184]

Wayne needs to wade in on this but, I think the hung start is due to the secondary fuel nozzles not providing fuel.

That's correct.

If the additional fuel does not flow it will hang up at whatever the max RPM available on the "start" fuel is. Typically maybe it will accelerate to maybe 20-30% and just set there.

~33% is typical during hung starts.

I don't know what the ITT will do.i

ITT is normal but rotation is assisted.

The low battery will simply not let the starter motor help the acceleration and can result in not enough air for the fuel being introduced resulting in a hot start.

The low battery fear is that it loses power after fuel is introduced and in incapable of maintaining rotation prior to self-sustain N1 RPM.

A hot start may continue into a normal start but simply exceed the max temps allowed.

The transient start temp limit (dashed red line on gage) is limited to 2 seconds.

At that point the damage may be done already.

Safe to assume that damage to pilot's underwear is fait accompli.

A hot start does not always mean a catastrophic failure right then. It depends on how severe, it may just show up as premature failure later. Perhaps a more expensive HSI.

Like most limitations, some slack is built in to these numbers. Sometimes the damage is obvious (upon inspection) sometimes not.

Dave I would guess you will be temp limited well before FL200 in winter or summer. I am not familiar with the -21 but would just GUESS on a standard day by 15,000, perhaps lower.

On even the coldest day for which performance charts are published (ISA-10) the 90's will only hold max torque though 8,000' before temp limits come into play, so for all practical purposes you can say that they are always temp limited.

Beech publishes performance to FL280 for the B-90 (same HP as Dave's plane) at ISA+40, so they think it will get there. Max available torque due to temp limit (temp limit is unstated in performance charts but shown as 725C in max cruise limitations section) drops from ~550# at FL220 to ~450# at FL280, and fuel flow drops from 325 PPH to 266 PPH. TAS only drops 3 knots, from 190 to 187.

I've flown Dave's airplane quite a bit (prior to his purchase) and remember one trip at FL240 as being ho-hum. I don't think he'll have any problem using higher altitudes and will appreciate the improved ratio of airspeed to fuel flow.

 

[ronnieh]

Wayne, just curious, with such a low altitude for temp limit does the -21 perhaps have only a 2 stage compressor?

 

[Dave Siciliano]

Thanks fellas. You're giving me great insight. Looking forward to the trip to Orlando tomorrow. I'll get some numbers on here when I can.

Best,

Dave

 

[wabower]

Nope, 3 axial and 1 cengrifugal. They're just not quite as stout (thermally speaking) as some other engines, and Beech decreed that they operate with greater margins than some of the other variants.

Wayne, just curious, with such a low altitude for temp limit does the -21 perhaps have only a 2 stage compressor?

 

[ronnieh]

By two stage I was refering to the number of axial wheels. I guess all the PT6's have three axial wheels? Thanks for the answer. I was too lazy to try and find the info.

 

[Dave Siciliano]

695 limit in my POH. Another inconsistency for the same engine?

Best,

Dave

 

[wabower]

Could be, and if so my fault for failure to note (in each post) that I was using the B-90 with -20 engines. You can't run them hotter than 695 either without risking premature engine work, but the book allows 725.

695 limit in my POH. Another inconsistency for the same engine?

Best,

Dave

 

[gismo]

Thanks fellas. You're giving me great insight. Looking forward to the trip to Orlando tomorrow. I'll get some numbers on here when I can.

Best,

Dave

Dave are you coming to Simcom tomorrow for Baron training? I'm currently at a water ski "camp" a few miles west of Orlando and will be headed for the Wingate Wednesday evening. I hope to see you there but figured you were focusing on the KA for now.

 

[TangoWhiskey]

I am in town, too. Will be here through Saturday, leaving Sunday. My wife will be here too as of Thursday evening...

 

[Dave Siciliano]

Yes, I got into Orlando a few hours ago. Doing baron recurrent on day for insurance, getting some Ka sim time, then joining the Advance Baron folks.

Small world Troy!

 

[Ted]

And from the looks of it, spent most of the flight at FL230. What'd you think?

 

[Dave Siciliano]

It worked out very well. Cabin was 9,000; a bit higher than I like but reasonable. TAS was over 220 at the higher power settings and we had a bit of a tail wind. Temps did shoot up a bit on the restart after dropping a passenger. The right hesitated a bit just over 20% then caught and ran up higher than normal. B
Didn't exceed any limits but I'm scratching my head as to why. Left started normally.
I'll be in the sim all day or classes today.

Dave

 

[Henning]

It worked out very well. Cabin was 9,000; a bit higher than I like but reasonable. TAS was over 220 at the higher power settings and we had a bit of a tail wind. Temps did shoot up a bit on the restart after dropping a passenger. The right hesitated a bit just over 20% then caught and ran up higher than normal. B
Didn't exceed any limits but I'm scratching my head as to why. Left started normally.
I'll be in the sim all day or classes today.

Dave

The only thing that I can think of is that since it was a hot engine it managed to boil off some fuel and passed a vapor block through a nozzle momentarily starving it for fuel; or you have a fuel system problem in it's infancy.

 

[Ted]

What's the cabin pressure differential on your C90, Dave? Just curious. On the Cheyenne, at FL200 we had a cabin pressure a bit below 5,000 ft. I want to say it was a 5.4 psi cabin, same as the Commander.

It is nice to be at or below 8,000 ft cabin altitude. Flying up to Newfoundland and back in one day, at FL250 I think we were around 8,000 ft cabin pressure (maybe 9,000). Coming home at FL200 (which made up about 60% of the flight hours) we were below 5,000. With 9 hours on the Hobbs in one day, I was still fresh. Quite a bit different from my standard 9 hour flying day, which would typically have me at 9-12,000 ft.

 

[wabower]

Was it a battery start? Was the first engine to restart the hotter of the two? Did you use x-gen assist to start the second engine? If yes to all, the pattern is fairly common.

It worked out very well. Cabin was 9,000; a bit higher than I like but reasonable. TAS was over 220 at the higher power settings and we had a bit of a tail wind. Temps did shoot up a bit on the restart after dropping a passenger. The right hesitated a bit just over 20% then caught and ran up higher than normal. B
Didn't exceed any limits but I'm scratching my head as to why. Left started normally.
I'll be in the sim all day or classes today.

Dave

 

[RotorAndWing]

What's the cabin pressure differential on your C90, Dave? Just curious. On the Cheyenne, at FL200 we had a cabin pressure a bit below 5,000 ft. I want to say it was a 5.4 psi cabin, same as the Commander.

It is nice to be at or below 8,000 ft cabin altitude. Flying up to Newfoundland and back in one day, at FL250 I think we were around 8,000 ft cabin pressure (maybe 9,000). Coming home at FL200 (which made up about 60% of the flight hours) we were below 5,000. With 9 hours on the Hobbs in one day, I was still fresh. Quite a bit different from my standard 9 hour flying day, which would typically have me at 9-12,000 ft.

One of the problems with older KingAirs are leaky cabins. It really pays to have a mechanic take the time to reseal and replace door and emergency exit gaskets. Just a few small areas sealed correctly will really bring the cabin down.

 

[wabower]

Cabin doors and seals definitely fall into the "not their strong point" category when discussing King Airs.

Emer exits on C's are more problematic than on B-200's and others due to design.

Leak-testing with a pressurization machine is interesting to watch. Lots of crayon marks on the structure when the test is complete

Pressurization function is easily checked by reference to gages. Aircraft altitude and corresponding cabin altitude are clearly marked, as is max diff.

One of the problems with older KingAirs are leaky cabins. It really pays to have a mechanic take the time to reseal and replace door and emergency exit gaskets. Just a few small areas sealed correctly will really bring the cabin down.

 

[Ted]

One of the problems with older KingAirs are leaky cabins. It really pays to have a mechanic take the time to reseal and replace door and emergency exit gaskets. Just a few small areas sealed correctly will really bring the cabin down.

Makes sense. I've been fortunate enough to fly pressurized aircraft that are well-sealed, so I didn't think about that.

So I guess the next question is really in two parts:

1) What is the max cabin pressure differential supposed to be?
2) What is Dave observing?

 

[ronnieh]

Machine is called a Huffer. We have the cabin checked for leaks once a year. 2-3 hours labor. When you stand beside the plane with even 3.5 PSI the shape of the windows and sheet metal gives you something to think about. Might be best if you did not look down the side while pressurized.

 

[Dave Siciliano]

Makes sense. I've been fortunate enough to fly pressurized aircraft that are well-sealed, so I didn't think about that.

So I guess the next question is really in two parts:

1) What is the max cabin pressure differential supposed to be?
2) What is Dave observing?

Ted: 4.6. At 20,000 our cabin is 7,000. We are seeing exactly what the gauge shows it should be. 230 was 9000. That seems to be the tradeoff, better fuel flow and range higher, better cabin and a bit faster lower. We were also topping some weather which made 230 the best choice.

Dave

 

[Henning]

What does it take to keep a 41,000' cabin below 8000'? 9.2lbs?

 

[Dave Siciliano]

N1 stabilized at 17 to 18 on battery alone, so, I didn't use generator assist. Yes, slightly hotter of the engines, but not by much.

Dave

 

[Dave Siciliano]

Flew the 58 sim today. Will get some KA and Baron time tomorrow. Great session today.

Dave

 

[Henning]

One of the problems with older KingAirs are leaky cabins. It really pays to have a mechanic take the time to reseal and replace door and emergency exit gaskets. Just a few small areas sealed correctly will really bring the cabin down.

Pressure vessel panel seals as well. Lot of work but worthwhile.

 

[wabower]

What does it take to keep a 41,000' cabin below 8000'? 9.2lbs?

About 8.4. 10.92-~2.5.

 

[Henning]

About 8.4. 10.92-~2.5.

What is the highest pressure Biz Jet product?

 

[wabower]

Dunno. G-V was somewhere around 10, can't remember exact number. Enough diff to maintain 6k' cabin at FL510.

What is the highest pressure Biz Jet product?

 

[Henning]

Dunno. G-V was 9-something, 6k' cabin at FL510.

Ok, that's where 9 some came from, I was not aware they certified that altitude, that's pretty interesting, I would love to get a ride through that altitude cycle so I could watch that engine performance cycle. That's running pretty close to the ragged edge.

 

[jhausch]

Dunno. G-V was somewhere around 10, can't remember exact number. Enough diff to maintain 6k' cabin at FL510.

Pretty amazing considering the big windows and age of that fuse design. I am assuming the design has evolved a bit over the years, but it is my understanding* that the basic fuse shape and design has remained constant (except for lengthening) because of the $$$ needed if there were a wholesale change.

*3rd party, anecdotal

 

[wabower]

I heard that for years as well, but the new cabin on the 650 seems to dispel the theory. Bigger tube, even bigger windows with same characteristic oval shape.

In addition to their increased size, the Gulfstream's big windows are set lower than most (on the midpoint) to provide passengers with an incredible view. We flew directly over the White House at cruise altitude on one fine clear day and I thought for sure I could see Lincoln's bed. When they were building one of the new planes for which I managed the acquistion and related stuff, one of the factory guys told me that Gulfstream had never experienced a window failure. I didn't check it out, but found it interesting anyway.

Pretty amazing considering the big windows and age of that fuse design. I am assuming the design has evolved a bit over the years, but it is my understanding* that the basic fuse shape and design has remained constant (except for lengthening) because of the $$$ needed if there were a wholesale change.

*3rd party, anecdotal