4 hours ago, Stoopy said:

Yeah but long before the engine quits shouldn't power output fall significantky enough that maintaining a climb is no longer possible?  In which case the aircraft would reach a point of anemic equilibrium? I'm not an aircraft powerplant expert but years of being a shadetree mechanic makes this scenario with the engines essentially choking themselves to death sound quite counterintuitive.  

Yes. It should be virtually impossible to kill an engine by just climbing and walking away. The power lost due to inefficient mixture settings should lead to a power drop off that would make a climb eventually impossible to an altitude where it WOULD just die. You should just end up at a max possible altitude where you can no longer climb BEFORE you get to an altitude where the engines can no longer even run. This is basic science and the whole reason we have step climbs. The plane stops being able to climb before the engines quit. 

UNLESS you deliberately sabotage the mixture by leaning to cut off point. Some one prove me wrong please! 

🤔

1 hour ago, sloppysmusic said:

This is basic science and the whole reason we have step climbs.

Steps climbs are not related to mixture or engine combustion failure (piston or turbine). Step climbs exist to burn fuel weight before the next step, so the thrust output exceeds the thrust-weight requirements by the time you get to the next step.

1 hour ago, sloppysmusic said:

The power lost due to inefficient mixture settings should lead to a power drop off that would make a climb eventually impossible to an altitude where it WOULD just die.

This is making the assumption that the power loss is linear, which it is not. The end of the power graph on the rich end is a very mild power decline, then a steep dropoff at combustion failure. At the corner before the transition you could certainly have plenty of power left for the climb.

It's hard to picture this from a naturally aspirated engine, to be sure. However, these old aviation turbo engine designs are positively dumping loads of fuel in to keep the charge cool enough, because the detonation margin is so slim, and so when you lose manifold pressure you end up about twice as rich as in a N/A engine. In fact, not only do you need to be careful not to outright flood the engine, it's vitally important to observe proper lean technique as there's actually a rich-side detonation region. We went through all this stuff when we modeled the SR22T custom engine systems to provide for these idiosyncrasies and failure points.

Here's Cirrus's turbo engine management slide deck, you can see page 23 where it mentions overrich flameout, and page 63 talking about detonation regions: https://cirrus.cz/files/sr22t_engine_operations_1_7272df3806.pdf

Edited May 15, 20242 yr by MattNischan

Its been a while since I took the non grand duke up to FL300 🙂

So I did hit the critical altitude just beyond FL250... the best way to notice the sharp power falloff is by looking at the HP on the EDM 760.  It starts to fall off passing FL253 or so (ISA).  So then I just continued a gentle leaning as I climbed and was able to get up to FL300 at 120 kias per the charts with ease.

Cruise at 75% power is darn spot near on!  (though the little gauge might not be calibrated for the right power setting at this altitude... it shows me and 55% or so on the analog)

(ATC forgive me for the vfr code in class A lol)

b60critical by Ryan Butterworth, on Flickr

b60cruise by Ryan Butterworth, on Flickr

1 hour ago, MattNischan said:

Here's Cirrus's turbo engine management slide deck, you can see page 23 where it mentions overrich flameout, and page 63 talking about detonation regions

Thanks for the info I shall read it soon.

Ok I have another question. Tonights flight I stuck to 24k cruise to be safe. Plane climbed well at full fwd levers and levelled off 24k. At this altitude only very minor changes were noticed by leaning so left it full. Until descent. 2000fpm descent after 500ft at 23.5 the engines died. I quickly grabbed mixture levers and dropped to 2/3 and engines fired back up. All the way down to 16k if I did NOT have them at 2/3 the engine would stall. I THOUGHT that up to 24 k mixture was irrelevant? Or at least negligible. Why  during climb to 24 did mixture levers work fine at full but the moment I started descending they took a huge hit and needed fast leaning?

Here are 2 screens showing the descent mixture effect:

22 hours ago, monica6211 said:

Don't do that!!! Get any one of the three mentioned above....you won't regret it!!! If it were up to me, definitely the Duke, then the 414, then the 310, in that order. But the 414 is a little easier to get going than the Duke. The Duke has to be handle more precisely, where the 414 is a little more forgiving, in my opinion. Of the 414 and 310, I personally fly the 310 a lot more than the 414. I feel more immersed in the cockpit of the 310 than I do the 414, plus I've actually flown the 310 a few times. You can't go wrong with any of them. The only way to go wrong is to stick with a single engine piston and miss out on the twins.😁

So which has the best view? Because that's honestly why I've mostly avoided twins for all these years - I like them but then I can't see much of the wonderful scenery (unless going external cam ofc, but who does that??).

7 minutes ago, s0cks said:

So which has the best view? Because that's honestly why I've mostly avoided twins for all these years - I like them but then I can't see much of the wonderful scenery (unless going external cam ofc, but who does that??).

I haven't flown the 414 in a while, but I can imagine the Duke has better visibility (those big engines block a lot). I haven't tried the 310.

2 hours ago, sloppysmusic said:

23.5 the engines died. I quickly grabbed mixture levers and dropped to 2/3 and engines fired back up. All the way down to 16k if I did NOT have them at 2/3 the engine would stall. I THOUGHT that up to 24 k mixture was irrelevant? Or at least negligible. Why  during climb to 24 did mixture levers work fine at full but the moment I started descending they took a huge hit and needed fast leaning?

I think what people are forgetting is that turbos are not magical MP boosting machines. They require high velocity exhaust gases to work.

When you pull the power back for descent (or when power starts to degrade at overly rich mixture settings in climb) the turbos slow down...
When the turbos slow down, they no longer make full boost...
When they no longer make full boost (and the absolute pressure gate is closed) the exhaust slows down...
When the exhaust slows down, the turbos slow down...
...and so the cycle continues until combustions stops due to overly rich mixture in ambient pressure air.

That's why the warning about closing the throttles at high altitude, and the only way to restart the engines is pulling the mixtures back. The same cycle can happen in a decent or any phase of flight if the turbos slow down too much to make a combustible mixture. The fact that this is simulated is really impressive, and leagues ahead of the Real Air versions, impressive as they were for their time.

7 hours ago, GACSavannah said:

No it was not. This has simply been a very busy week. I do need to get you the terminal pictures. One thing that you can do in the mean time...Image No. 20, you can take the large Gulfstream Hangar, make a mirror of it, and place it to the right side of the office block that you currently have on the right side, as we have just completed doubling that hangar.

Excellent. Then get me pics asap. If you have a pics of the hangar doubling you reference that would be extremely helpful as well for placement purposes. Obviously it is not shown in Google Earth.

Thanks,

Mitch

3 hours ago, mmcmah said:

I haven't flown the 414 in a while, but I can imagine the Duke has better visibility (those big engines block a lot). I haven't tried the 310.

I meant to say that I CAN'T imagine that the Duke's view will be better than the 414.

2 hours ago, mmcmah said:

I meant to say that I CAN'T imagine that the Duke's view will be better than the 414.

It has always been my favorite IFR training aircraft for that reason! The Duke I mean. 

5 hours ago, BennetHill said:

When the turbos slow down, they no longer make full boost...
When they no longer make full boost (and the absolute pressure gate is closed) the exhaust slows down...
When the exhaust slows down, the turbos slow down

That's very interesting. I'm only familiar with car turbos which are tuned for a particular rpm and suffer lag spooling up to it. Is an aircraft turbocharger also tuned to rpm or mp or both? Sorry to ask if it's in manual as missed it but what I'm asking for is what rpm and mp to set BEFORE I start descending from CA in order to completely avoid engine failure. I don't want to wait until I lose power suddenly at all if possible. Not drastically anyway. 

9 hours ago, MattNischan said:

Here's Cirrus's turbo engine management slide deck, you can see page 23 where it mentions overrich flameout, and page 63 talking about detonation regions: https://cirrus.cz/files/sr22t_engine_operations_1_7272df3806.pdf

Thanks, this is a great reference!

I've been reading Mike Busch's book "On Engines" -- I've learned a lot from it and would highly recommend it to anyone. The Black Square Piston Duke and the discussion here have been really useful in helping me understand how the principles of turbocharged engines that Mike describes in the book play out in actual operations. Like others, I expected I'd mostly fly the Turbine Duke, but the piston version now interests me more because of all of the quirks related to turbocharger operation.

19 hours ago, martinboehme said:

I did another test in the meantime, but bringing the mixture back as soon as my manifold pressure started falling. I was able to make it all the way up to FL 290 without any issues. Fuel flow at this point was about 200 pph on both engines. Referring now to the manual, I see that I should probably have brought it back quite a bit lower. Looking at the chart for 75% cruise power, I see that at a manifold pressure of 34.1 inHg (which is about what I was getting), fuel flow should only be 133 pph.

Interesting discussion. Randomly quoted this paragraph, lots of useful information here. 

So, is it safe to assume that when manifold pressure starts to drop, we’ve passed the critical altitude? 

Also, I was not aware that it’s possible to climb the piston with prop full and throttle wide open. Guess I’m a bit confused re: differences in engine operations piston vs turbine. And perhaps also turbocharged piston vs “regular” pistons.

I’ve only climbed to 24,000 in the piston (Grand Duke), so haven’t experienced the engine failure at exactly 25,000ft.

Disclaimer: didn’t finish reading the rest of the thread before posting (was worried that I would forget what I was going to say…)

18 hours ago, Treetops45 said:

For the Turbine version - looking for the COWL Flap Open & Close click spots. (Ideally, a pic)

It’s probably been answered (and I don’t have a pic), but it’s in between the switches. Click, then “drag” both switches simultaneously either up or down. Either use a timer set at 14 seconds (realistic), or look at the engine page of the EFB.

As for the misbehaving/inaccurate clickspots that sloppy mentions, I haven’t experienced that. The one to the right of the ALT select knob seems to work - I scroll mouse wheel forward, nose goes down. And vice versa. 

Edited May 16, 20242 yr by Cpt_Piett
Finished reading the rest of the thread

As  for the visibility question - the 310 is best followed by the 414 & then the Duke.

I love hand flying ILS approaches (do several every week) so was super pleased when the 310 was released (never liked the Baron either in R/L or in the sim) - used that until the 414 came along (have many thousands of hours on both those) then along comes the Duke (which I never had the chance to fly but admired their looks).

Now when it comes to ILS flying I found that the 414 had a far better instrument layout than the 310 - so went along with that - but the biggest problem I have had with the 414 was getting it trimmed correctly for the descent. Always was hard (maybe a better description would be that it was annoying not being able to get the trim right & stable) & also it was easier to keep the engines in sync on the 414 rather than the 310 - which was better to trim.

So now comes along the Duke - great instrument placing & visibility when you get rid of the control columns. As for visibility it's  not a great problem for me when I don't look outside on the approach anyway (always fly it at night & in cloud to make it more fun) - now the Duke has become my favorite mainly because the trim is so much more responsive & I can set it up nicely for the approach. Will also be practicing more engine failures when I get really on top of it - didn't do many with the 414 because of the trim problem (maybe the trim problem is something to do with my control setup - Honeycombe throttles & F18 grip allied with a real sim FSSB base.

The biggest bugbear for the Duke for me in these excercises is that trying to keep the engines in sync - is the worst of the 3 but other than that it's my goto twin for flying the ILS (Commnache for the S/E)

46 minutes ago, Cpt_Piett said:

So, is it safe to assume that when manifold pressure starts to drop, we’ve passed the critical altitude? 

Yes, this is essentially the definition of critical altitude. From the manual:

Quote

Simply put, the critical altitude of a turbocharged engine is the maximum altitude at which the turbocharger can compress the atmospheric pressure air to a specified maximum pressure. When the aircraft continues to climb beyond this altitude, manifold pressure will begin to drop, and the mixture must be leaned, just as with a normally aspirated engine. Critical altitude is listed in aircraft handbooks as a single altitude in feet; however, critical altitude as described above, is constantly changing throughout the flight.

 

46 minutes ago, Cpt_Piett said:

Also, I was not aware that it’s possible to climb the piston with prop full and throttle wide open. Guess I’m a bit confused re: differences in engine operations piston vs turbine. And perhaps also turbocharged piston vs “regular” pistons.

You can do this in the piston Duke, but this may not be true for other piston airplanes.

46 minutes ago, Cpt_Piett said:

I’ve only climbed to 24,000 in the piston (Grand Duke), so haven’t experienced the engine failure at exactly 25,000ft.

Note that the critical altitude won't always be exactly 25,000 ft (see the manual quote above), and the engine won't quit at exactly the critical altitude (if you don't lean).

IIUC, the value for the critical altitude noted in the manual applies in ISA conditions. If conditions are non-ISA, the critical altitude will be different (and this is modeled in the Piston Duke). I suspect the critical altitude may always occur whenever your density altitude reaches 25,000 ft, but I'm not sure about this. At any rate, it's easier just to watch for the manifold pressure to drop rather than trying to calculate what the density altitude is on the day.

Edited May 16, 20242 yr by martinboehme