Twin Otter Crash May 20, 2023

[TrilliumFlt]

Finally there are bladder systems. These are lighter, but every one I've seen requires fuel pumps which are run off ship power. They are independent of the boost pums. The system I used had 4 independent pumps and I want to say that 2 could keep up with fuel burn of the engines.

How does the dump system work for the bladders?
Ditching with full ferry tanks would be very undesirable.

I can't speak too the bladder setup; I've only used hard tanks, neither the deHavilland drum setup or the larger fuselage tanks have a dump system per say you just burn fuel no dumping.

[propfeather]

Finally there are bladder systems. These are lighter, but every one I've seen requires fuel pumps which are run off ship power. They are independent of the boost pums. The system I used had 4 independent pumps and I want to say that 2 could keep up with fuel burn of the engines.

How does the dump system work for the bladders?
Ditching with full ferry tanks would be very undesirable.

I can't speak too the bladder setup; I've only used hard tanks, neither the deHavilland drum setup or the larger fuselage tanks have a dump system per say you just burn fuel no dumping.

Having done many trips with the dual hard tanks (1850L total), with a dump valve, I wouldn't be very comfortable without a dump system.
I thought that was a requirement but shows you what I know.

[TrilliumFlt]

How does the dump system work for the bladders?
Ditching with full ferry tanks would be very undesirable.

I can't speak too the bladder setup; I've only used hard tanks, neither the deHavilland drum setup or the larger fuselage tanks have a dump system per say you just burn fuel no dumping.

Having done many trips with the dual hard tanks (1850L total), with a dump valve, I wouldn't be very comfortable without a dump system.
I thought that was a requirement but shows you what I know.

The LSTC may very well have been revised since I last used it to install the ferry system, as I said that was a former life. It certain would add a level of comfort, I've been forced to turn back and land overweight twice due to a "do not proceed any further" issue.

[Rowdy]

Also having ferried a considerable number of Dhc6's around the globe...

The two Hard tanks indeed require a dump. I always wondered about it, as a V1 cut or low level engine failure would be a disaster if you had to climb back there, kick the door open, push the hose out and then swing the valve.. but.. I'm no expert.

I only ferried one time with the bladders. Also had a similar dump system. Not sure I have a preference.

Both were incredibly simple. Pretty hard IMHO to screw up. Makes me wonder what happened to cause the fuel starvation.

On many of the ferries, we also carried a bleed line with a quick connect (if a/c so equipped) or a wobble pump and an extra drum or two. In the event you ran into issues, you'd go back and blow the drums into one of the ferry tanks buying you an extra chunk of time.

We also always carried an o2 bottle and masks so we could scoot up above 12,000 and get the fuel burn down further.

I was taught to burn down to 3/4 in the mains and then crack the valves and match the fuel flow from the ferry tanks to the fuel burn. Every couple hours, one of us would go back with a stick and flashlight and check the hard tanks.

Longest leg I did was 12hrs. Full mains, Tips, Hard tanks and a drum.

We always ferried on wheels. Be silly to run floats/amphibs on the long legs. Also much more of a pain on intermediates or tundras.

I cant comment on this incident as I don't know any more of the specifics than anyone else. In the end, two of our comrades lives were lost. Sad day indeed. My respects and condolences to their friends and families.

[TrilliumFlt]

I've used the deHavilland "barrel & ladder" setup and a third party LSTC, neither had any pumps associated with the installation. All fuel gravity fed to the main tanks and thereafter via the airframe fuel system to the engines. To "prove" fuel flow to a regulatory agency it was a simple matter of opening the ferry tank valves, turning on battery power and watch the main fuel gauges increase in quality as the fuel flowed into them.