Mi-8 Failures

[JBM]

I just spent 40 minutes in the Convoy Raid mission. My rockets took out the two convoy gunners, and my onboard gunners were happily dealing with the rest of the convoy.

There were three convoy vehicles remaining, and as I was positioning the heli for the side door gunner, I had warnings popping up for Main Fuel Tank Pump Failures.

Checking the overhead console, the left and right fuel boost pump lights were indeed out, so I landed and performed a shutdown.

In the debriefing however, there was no mention of ANY failures.

Anyone else had this?

[eca001]

i usually heard it when low on fuel, maybe a fuel leak?
like when around 10~20% fuel left

[spike2071]

I think it means you're out of fuel in the left and/or right tanks. The one time I had this alert I checked the fuel gauges and the left and right tanks were indeed empty, but the service tank had some fuel. I turned off the left/right pumps and had enough fuel to continue my flight home.

[edit]

I found this link with a detailed pdf:

https://forums.eagle.ru/showthread.php?t=151933

[/edit]

[JBM]

Originally posted by eca001:

i usually heard it when low on fuel, maybe a fuel leak?
like when around 10~20% fuel left

By the time I had thought about fuel levels, I had already ended the mission! Possible lesson learned. ;)

Originally posted by spike2071:

I think it means you're out of fuel in the left and/or right tanks. The one time I had this alert I checked the fuel gauges and the left and right tanks were indeed empty, but the service tank had some fuel. I turned off the left/right pumps and had enough fuel to continue my flight home.

[edit]

I found this link with a detailed pdf:

https://forums.eagle.ru/showthread.php?t=151933[/edit]

I gave some thought to fuel levels afterwards, and I guess I had been flying long enough to use a fair amount of fuel. I'm sure sustained low level hovering and pulling collective in sharp turns would burn through it in no time.

Bearing all this in mind, I would still have expected the "pump failures" to show up in the debrief, which showed no failures at all. It's a little perplexing.

That PDF doc is very useful. It also answers some questions I had about fuel tank feed connection arrangements and shut off valve locations. so thanks for that!

[spike2071]

Originally posted by Jim Bob:

Bearing all this in mind, I would still have expected the "pump failures" to show up in the debrief, which showed no failures at all. It's a little perplexing.

I think it's because the pumps didn't actually fail. The alert went off because they were no longer pumping gas from the tanks to the engine (which could mean a failure), but it was actually due to no gas. A mechanical failure would've shown up in the logs, but the pumps were fine.

Just like when the generators fail due to low blade RPMs. That doesn't show up in the log because there's nothing mechanically wrong with the generators. Take some AA through them, and the generator failure shows up in the debrief (usually right before it says, Pilot Dead). :)

[JBM]

Originally posted by spike2071:

I think it's because the pumps didn't actually fail. The alert went off because they were no longer pumping gas from the tanks to the engine (which could mean a failure), but it was actually due to no gas. A mechanical failure would've shown up in the logs, but the pumps were fine.

I think this is exactly it. I will admit, until I read the PDF you linked me to (and then had a scan through Chuck's Guide to the Mi-8), I never even knew until now that the fuel level selector knob was actually functional in the sim!

So having just flown the mission again, I can now confirm that the pumps do indeed "fail" due to the left and right tanks becoming depleted. Turning the knob to view the fuel level in the desired tanks shows them as empty.

Now I know!

Thanks for your responses! :)