2 questions. Props @ 2100 RPM and Turbo Calibration.

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TreeTops
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2 questions. Props @ 2100 RPM and Turbo Calibration.

Post TreeTops »

So after a very long period of time I decided to get reaquainted with the Strat. I didn't fly it much after COTS release because of many reasons, one being the flights were too long!
So, to the questions.

1.
At 30,000 ft and setting up the cruise (mid loadout & fuel) I noticed an issue with the prop sync. For basic recommended settings of 40" and 2100 RPM, I was at full throttle and using turbo lever to give 40". Pulling back the props from 2350 RPM climb to 2100 RPM cruise caused engines 2, 3, 4 to hunt for Engine 1 RPM, fluctuating about 300 RPM. I eventually figured out that 2100 RPM was the cause and setting 2250 or even closer to 2200 RPM stabilised the 3 engines to hold sync with engine 1. I let it fly around for about 3 hours last night and on each occasion i tried to set 2100 RPM the same fluctuations occurred. Prop check had been performed on the ground without issue.
Any thoughts on why 2100 RPM couldn't be achieved?

2.
I have trouble with the procedure of cailbrating the turbos after start up (at near to sea level).
From the COTS check list
7. Place the turbo selector lever to 0 (zero), the respective turbo control override switch to CLIMB & CRUISE; move turbo boost lever to 7 and align the calibrating potentiometers; check for a manifold pressure increase of 2 inches plus 1.5 inches for each 1000 feet of field altitude above sea level; place the turbo control override switch to TAKEOFF and note that exhaust back pressure and manifold pressure return to their original values; then move the turbo-boost lever to 0
The way I read the procedure was to start with the turbos switches set to take-off, engine 1 at 30" (ambient atmos pressure), engine 1 turbo switch to climb, move the turbo lever to 7 and adjust the calibration to approx 32". The problem I had was the engine ran up to max power and the engineer was in my ear about the engine getting hot.
Can someone please explain where I am going wrong as it shouldnt be a difficult procedure.
Cheers
Trev

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Jacques
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Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post Jacques »

Hi Tree,

I can't really speak to the issues with RPM that you experience at 30,000 feet. I only ever tried to reach that altitude during my first flight in the Stratocruiser, and that was a few years back now.

With regards to the engine check on the ground, I have to admit I'm right there with you! The only thing I might mention about the check and the temperatures you are getting is to be sure you have your ADI on and set to AUTO. I also realize that you are only supposed to check that the light extinguishes, and then you are to turn the ADI off, but I left mine on to prevent damage. Also, pointing the aircraft into the wind is the first item on the list.

I have never been able to complete this test because my results duplicate yours-- they are so far off from what is expected that I stopped trying to perform it after the first few flights. I tried again today at KABQ, about 5300' elevation. Barometer indicated 30.23". I isolated number four, switch set to "takeoff", turbo pot set to the white hash mark, turbo control lever at Zero. Ran number four up to 30.2" with the throttle, checked RPM at 2100, move switch to climb and cruise, advanced lever to 7 (70% ?) and the MP goes way up to past 60". According to the manual, I should expect a rise of something just over 40". No amount off moving the potentiometer will move the MP off of +60".

I try to fly the Stratocruiser by the manual and as realistically as possible, so this has always bothered me that I haven't been able to complete a careful ground check of the engines!

I'm with Tree, what are we doing wrong?

JP


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Jacques
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2 questions. Props @ 2100 RPM and Turbo Calibration.

Post Jacques »

Tree,

I found an answer in an old post to the second of your questions:
Scott - A2A wrote:You don't need to go all the way to 7 on the turbos, we scaled these more linearly than the real plane due to simple limitations with controllers. This basically makes it easier to get a nice smooth turbo operation.

Just advance the throttles to about 30", then advance the turbo until you see a boost and tune. You can do this as low as 32" I go to 35".

Scott.
Edit-- I tried half fuel and mid-weight load up to 30,000 ft. Everything behaved as it should during the cruise-- 2100 RPM, 158PSI.

You should set your power settings first by MP, then by the required torque setting. Could that be the cause?

I messed around with different settings and the only thing that caused any kind of RPM fluctuation was a serious reduction in power to any given engine, which allowed the wind to drive the prop. Curiously, when I reduced power to all four engines and left the props unfeathered, you could hear a whine from the props that rose and fell with the fluctuation in RPM.


JP


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TreeTops
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Posts: 810
Joined: 07 Apr 2010

Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post TreeTops »

Thanks for your responses JP.
I forgot to add that yes I was pointed into the wind at the time of run up tests.
Thanks for remembering the point Scott made about not setting the lever to 7. That is the obvious one isn't it. FAQ entry to be made? So the procedure should read the same except to advance the turbo lever to a mark of 1,2,3 etc to indicate something like 2-5" above ambient pressure adjusted for airport altitude. Read off the MP with the calibration at 0, then set the other engines to match that MP with the turbo lever at the same location as the first engine. I think that makes sense.

Last night I had time for a slow descent from 30,000 to 6,000 and getting down I had to raise the prop RPM to about 2350 over time since the hunting problem limit was climbing from 2200 to 2300 as I got lower. I was holding 2" boost and holding 40" using the throttles with all adjustments kept small.
I think another flight before i get too concerned about the props :)

Tonight I will land and begin another flight to try the turbo setup.
Thanks again for your help.

Trev
Cheers
Trev

BraselC5048
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Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post BraselC5048 »

I actually had the same problem, and I perform the check by reading it a little differently. Instead of setting the turbo level to 7 on the stand, I advance it to 7% (via tool tip). The gives a MAP increase to about 32-33". Also, I aligned the turbo calibration (tool tip helps) at cruise on the first flight after an engine is overhauled (read: my first flight), and generally leave it there.

TreeTops
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Posts: 810
Joined: 07 Apr 2010

Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post TreeTops »

An update for flight #2.

Setting the turbo levers to 7% approx gives around 2 psi on the turbo calibration so that advice makes sense. All turbos calibrated to 32" MP now (at near sea level).
After setting into cruise on the second flight I had no trouble reducing props to 2100 RPM, so this is making me wonder what was wrong on the first flight. No engine overhauls and the engines had 8.1 hrs after the previous flight.

Anway, moving onto to my next issue which is a lost engine. My fault for letting the centre tank run dry while AFK. :)
I managed to get engines 2,3 4 started but lost engine 1 for some reason. At least I managed to get it feathered.
I am feeling much more confident after the second climb and now have most things back in memory which makes it easier for targeted study.

Thanks for the assistance and advice.
Trev
Cheers
Trev

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Neon
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Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post Neon »

I usually calibrate the props only at cruise. I have done it on the ground
however it seems to work better at cruise once the plane has reached
it's cruising speed. It seems to work nicely then.

TreeTops
Technical Sergeant
Posts: 810
Joined: 07 Apr 2010

Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post TreeTops »

I might be wrong but something is reminding me of a conversation when this aircraft was first released.
It was something about the problem with tuning or balancing anything in the air is actually disguising a possible problem.
Tuning on the ground was the only way to ensure all engines / turbos / props / lever positions were where they should be.
Others might pitch in here with much more knowledge.
Cheers
Trev

TreeTops
Technical Sergeant
Posts: 810
Joined: 07 Apr 2010

Re: 2 questions. Props @ 2100 RPM and Turbo Calibration.

Post TreeTops »

Just to finish this post off answering the prop fluctuation issue, this was also experienced in the Connie.
The problem was with the propsync control assigned as mute in FS2Crew Q400.
Cheers
Trev

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