Engine start procedure fails above abt 4000 ft

[rudi0310]

Hi guys,

manual engine start fails for me above 4000 ft altitude. Ctrl + E works (most time). Varied various settings like throttle and primer, no solution, but might be my error.

Although I did not read anything about that so far, is this an already known issue? If not, I might make a video showing the problem.

Stupid question, because I'm new to MilViz' products: I heard a first service packe is in progress? How find I out, if an update is offered? Running MVAMS? News at the homepage?

Cheers
Rudi

[doodlebug]

Running MVAMS will get you the minor updates.. If there's a major update, you'll get notification via email with a download link.

[rudi0310]

Hi,

I can provide more info.

It seems that the animation of the ignition switch not always reflect its real position. Or needs a 'reset'. This leads to the observed strange behavior.

I can reproduce the problem in the following way (MVAMS: State: cold and dark):
- reload the aircraft in the P3D-vehicles-select vehicle menu
- do everything according to normal engine start checklist exept touching the ignition switch, which already is shown in position 'both'
- first try: turn starter switch on
- strange behaviour: Prop increases to abt. 2300 rpm within a few seconds. But engine does not start, starter switch does not return.
- manually switch starter off
- turn ignition switch in another position, then back to 'both'.
- second try: turn starter switch on
- now engine starts

Before second try, during my tests in some cases I had to reprime and/or use wobble pump. But the strange behaviour described above disappeared in every case after turning ignition swich to another position like 'both', then back to 'both'.
Tested with P3D V2.5 at an altitude of 6416 ft.

This effect has nothing to do with the altitude of the aircraft, as I thought first. In this point, I was completely wrong.

Cheers
Rudi

[Taguilo]

Engine start on the first try is not always assured, it depends on many factors.
Starting with Mags in both is not the recommended procedure, you need to first let the props rotate a bit with Mags off, then turn to Both and engine should start smoothly.

And yes, sometimes you need to wooble and reprime for a second start to succeed.

Tom

[Fliger747]

By way of explanation, it is typical of radial engines to only prime the upper cylinders. In the nine cyl. Beaver the top five are primed. For the R985 the passage of six blades is normal before engaging the mags, the idea is to distribute the fuel vapor and get some carb originated mixture into the bottom cylinders as well. With a cold engine it can take a while to get a quorum of firing cylinders. The acceleration pump feature of the throttle lever can be used to help introduce extra fuel, but this is with some hazard of spectacular backfire. The start setting of the throttle at 1/4" advancement is quite important!

[Hangar200]

Speaking of "spectacular backfires"…

Just flew a cold WX flight with light icing at ground level in light snow. As I ran up the engine for takeoff I started to get near continuous engine backfires. Once airborne I turned on carb heat and the backfires went away.

I'm a Mechanical Engineer so I understand why such a thing might happen in that environment. That said, carb heat does rob an engine of some power. I'm not a real pilot, however, what I have read on the subject is that taking off with carb heat on is generally not recommended…perhaps taxi with carb heat on but turn it off for the take off and initial climb.

By the same token, an engine experiencing continuous backfires is not putting out all the power it can so…

For this DHC2, what is the recommendation?