Plug fouling.

[DHenriques_]

Just tested, was able to pull a 25 second Idle this time.

One thing that might be causing this is something you might wish to consider. Merlins don't live well at all, as do ANY high performance engines, with the throttle back against a FULL idle stop! This might very well be your problem in a nutshell. Once started, you absolutely HAVE to keep at least 800 to 1100 RPM's on the engine to keep things running smoothly. Bringing a throttle all the way back to the idle stop can easily start an internal issues problem within these engines.
So try starting with a clean and overhauled Merlin, make sure all your expendables are full, and as soon as the engine starts, ADVANCE the throttle to a good sound and smooth idle RPM. You won't see it on the tach but you can "feel it" and hear it when it's right.
See if this helps!
Dudley Henriques

Right, I think we got lost back at step one. my reference to the engine dieing is at the idle stop. normally I give it more than that, but for aide in taxiing, slowing down, and just ground operations in general. While I wouldn't expect the engine to be thrilled at the idea of going back to 600~ RPM or so (Heck, both lycomings and continentals run rough at these RPMs) my thought is under these circumstances the engine should do better than 25 seconds?

In the Mustang for example, you find a "sweet spot" where the Merlin idles smoothly and the Spitfire should be the same. I wouldn't be surprised at all if a Merlin simply quit and fairly quickly with the throttle back beyond that idle sweet spot. Below that point, everything in the engine begins "working" and getting out of sync in one way or another.
Think of a Merlin as a finely tuned watch.
Try another start with the above in mind and see if the engine quits on you.
DH

[alehead]

Thanks for the tips and handling comments Dudley. It is a privilege to be able to profit from your experience here!

I find the climb out the most critical engine temp time for me now. I seem to be able to manage the Merlin well enough in terms of temperatures in other regimes.

Once I have the Merlin ticking over, I get to that 800+ rpm and all is well. I even noticed a small drop in radiator temperature if I get the flaps up fast and get a good taxi roll started and then pull the throttle back slightly.

I go below that 800+rpm band and she starts coughing and spluttering, with smoke and so on. It takes only a few seconds for the engine to react to too low an idle rpm setting.

Andrew

[DHenriques_]

Thanks for the tips and handling comments Dudley. It is a privilege to be able to profit from your experience here!

I find the climb out the most critical engine temp time for me now. I seem to be able to manage the Merlin well enough in terms of temperatures in other regimes.

Once I have the Merlin ticking over, I get to that 800+ rpm and all is well. I even noticed a small drop in radiator temperature if I get the flaps up fast and get a good taxi roll started and then pull the throttle back slightly.

I go below that 800+rpm band and she starts coughing and spluttering, with smoke and so on. It takes only a few seconds for the engine to react to too low an idle rpm setting.

Andrew

Great that things are working well for you. Just like the real one, the A2A Spit should run well if flown carefully and correctly.
A few things; keep the flaps up all the time while on the ground. Nothing will skew your temp limits faster than having them down on the ground.
On your climbs, you can play your radiator position, your power setting, and your airspeed in your cooling equation. Watching and monitoring your airspeed in the climb, you can vary it using a sawtooth pattern to effect cooling change as you go upstairs.
Enjoy!
DH

[Scott - A2A]

Andrew,

This post prompted us to make a short little video on how it is to idle these high performance prop engines, in this case the Merlin. During development we suspected that some clarification would need to be made since many sim pilots are used to pulling the throttle back to the stops and the engine continues to idle. This may have something to do with the fact that in many sims, an engine is either ON or OFF, and this would be odd to just have the engine ON, with a nice idle sound, then BANG, you hear the shutdown sound without warning.

Since Accu-Sim models all the internal components, there really is no ON / OFF state. You can use your ear to know how the engine is idling. You can feel it sort of drop off, then have to catch it in time before it dies.

Here is a little video excerpt from some engine sound recordings we were taking while researching the P-51D Mustang:
[youtube]http://www.youtube.com/watch?v=UkGEWZo2lsM&hd=1[/youtube]

Scott.

[CodyValkyrie]

Speaking strictly from a non-technical standpoint, I believe a lot of the Lycomings and Continentals of today are specifically tuned to a specific idle for just this reason. Many you can idle with the throttle at the backstop almost all day long without issue. I flew an old Lycoming powered 172 however when I was working on my PPL that would quit if it idled below 800 RPM if I remember correctly. There was a label that someone had put above the RPM indicator to warn pilots, as often guys would chop the throttle to bring the plane down. This plane had a lot of temper for a 172.

[alehead]

Thanks for this... learning more in the last couple of days than I have in the last few years concerning engine management!

Andrew

[Killratio]

Speaking strictly from a non-technical standpoint, I believe a lot of the Lycomings and Continentals of today are specifically tuned to a specific idle for just this reason. Many you can idle with the throttle at the backstop almost all day long without issue. I flew an old Lycoming powered 172 however when I was working on my PPL that would quit if it idled below 800 RPM if I remember correctly. There was a label that someone had put above the RPM indicator to warn pilots, as often guys would chop the throttle to bring the plane down. This plane had a lot of temper for a 172.

Cody,

as much as it pains me to say it, you are right!!

It is very uncomfortable, isn't it, when a lycoming quits at idle? I had it happen to me with only an hour solo under my belt. The aircraft had been serviced and the idle had been inadvertantly set too low. When I idle checked her, she stopped. I restarted and tried again, she stopped. After the third time I aborted the flight.

When I taxiied in the instructor the insructor wanted to know what the hell I was doing to his aeroplane. I told him and he checked it. It stopped. Undeterred he patted me on the shoulder and said "she won't stop on you in the air...off you go young'un."

As I got restarted and was about to head out, there was a knock on the window. It was him. I lifted the cans and he yelled to me ... "do you want to be BURIED or CREMATED?"

It was a VERY long hour of circuits for a young pilot!!

If you're reading this mate, YOU know who you are, I promise not to post the picture of you waking up floating horizontal a foot above the back seat


Darryl

[CodyValkyrie]

LOL! Good story.

My flight instructor quite literally was only a year or two older than myself. We actually hung out, same age group and all. He had graduated from his college and received his commercial rating and was trying to build up hours as a CFI. I will say however that while he was professional and always in control, I probably would have liked someone in that cockpit who was older, more experienced and slightly grizzled.

[Killratio]

slightly grizzled.

He WAS that!!

He is a funny man, too funny. We were on one nav at 43C OAT at ground level and flying over "Tiger Country" Bumpy as hell.

I had had, let's say, some bad "food" the night before. I started to feel a bit off so Funny Man starts discussing all sorts of tasty subjects. After 5 minutes I was getting close and he showed no signs of quitting...so I leaned over into his lap.

"what ARE you doing??"

Well, you have about three seconds to stop or I'm going to throw up and THIS is WHERE I'm going to do it!!

He quit, I kept it down and I got 100% for that nav. Great guy, I miss those days!!


Darryl

[JoeS475]

I had the same instructor type as Cody... He was 20 and I was 17... my 2nd instructor was 18 when I was 18. I didn't think much of it then, but looking back now I can't help but think of 2 18 year olds zooming around in a Cessna... Scary!!!! I had one very 'grizzled' instructor named Hal. Must've been in his 80's, and apparently if it flew, at some point he flew it! I believe he ferried fighters for the US Navy in WWII and then flew corporate until he retired and became an instructor. Sadly he was killed a few years ago in a checkride with a pilot who hadn't flown for a while, I believe they clipped some power lines on final... terrible loss of an amazing person and pilot.

I love hearing stories of peoples flight training, it brings back some fond memories!

Joe

[redberon2003]

During development we suspected that some clarification would need to be made since many sim pilots are used to pulling the throttle back to the stops and the engine continues to idle.
Scott.

Not just sim ones, but licensed ones as well. Hence my Lycoming/continental reference, while they are quite distant in relation to the Merlin, minus engine troubles or oddities (as cody seemed to underline above). once warmed I can full idle them for quite a long time before they reach the point of fouling beyond no return. and while again, the Merlin is a distant relative of these engines. It certainly struck me as odd that it would get fussy at the idle stop so quickly. My general taxi procedure as falls under my airman's license is to apply the power to get it rolling, keep a bit of power until I hit a brisk jogging pace, and then throttle back to idle. With turns brakes are used very sparingly, and so I'll pull the the throttle back to a full idle 50 yards off or so from the turn in place of wearing down my brakes.

Can't do it in the merlin .

That said, Dudley's seemed to confirm this would be typical of the Engine - so I don't know what else to say besides its time to find myself a new way to taxi lol (for the sim anyway). I otherwise find the airplane wonderfully modeled and it's been a pleasure to have a little taste of the Mark 1 in all of its 1930's Glory. Thank you both very much for your help.

[Killratio]

"New way to taxi"

Yes mate, the Spit really wasn't designed to taxi. She will do so at a brisk walking pace with plenty of throttle jockeying.
The pilot's notes seem to confirm this with an admonition NOT to relax throttle friction even if it will make taxiing easier.

I've seen a P-51 taxiied a few times and it was always done with bursts of power...probably for reasons Dudley gave above.

Anyhow, glad you have had it clarriffied to your satisfaction.

Oh, remember..stick back in the pit of your stomach at all times on teh ground until weight eases on wheels during takeoff run..that makes taxiing easier too..


regards


Darryl

[Bleddyn]

Oh, remember..stick back in the pit of your stomach at all times on teh ground until weight eases on wheels during takeoff run..that makes taxiing easier too..

That is the one I am trying to remember. I usually do just as the tailwheel is coming up under braking. It's not that it is counter intuitive at all, it makes perfect sense. It is just years of bad simming habits catching up with me.

Besides being fun this crate has been a hell of a learning experience.

[Killratio]

[. It is just years of bad simming habits catching up with me.

Yep,

And there is the exact point. I remember well having to overcome 6 years of bad habits through simming that I had to overcome when learning to fly.

Now years later, the Accu-sim systems are starting to make people "pay" for their mistakes earlier!!

regards


Darryl

[r4y30n]

Speaking strictly from a non-technical standpoint, I believe a lot of the Lycomings and Continentals of today are specifically tuned to a specific idle for just this reason. Many you can idle with the throttle at the backstop almost all day long without issue. I flew an old Lycoming powered 172 however when I was working on my PPL that would quit if it idled below 800 RPM if I remember correctly. There was a label that someone had put above the RPM indicator to warn pilots, as often guys would chop the throttle to bring the plane down. This plane had a lot of temper for a 172.

Now here's something I wonder about from an engineering standpoint... Since all these high performance engines are unhappy back at the idle stop then why couldn't the minimum idle be set from the factory to 800-1100 rpm so that the engines could go no lower?