Seeking DHC6-300 info

[Cool banana]

I been told that in Canada the DHC6-300 is approved to operate MTOW in the aerial work category is 14,400lbs?
And that Transport Canada will issue individual permits to go as high as 17,500 lbs for crew only ferry flights?

If this is the case where can I get official confirmation about the above matter as couldn’t find any think on the FAA or Transport Canada website, In Australia we are informed that the MTOW for the DHC-6 was only 12500lbs.

Any information would be greatly appreciated.

CB

[V2+ A Little]

Might get dispenasation, but not sure those weights are wise when things go wrong!!!!!!...................in a twotter!!!:}

[pitotman]

Cool Banana,

I flew the twin otter on a fairy flight back in the '90s and I no we were atleast 17,500lbs. If I was you I would contact someone at Kenn Borek Air as they are one of the worlds largest twatter operators in the world and they ferry a/c all over the world!

I have no experience in aerial work and I would imgaine that the 14,400 is not unreasonable for the a/c. I am sure on more than one occasion the floats on our twin otters tipped well over 12500.


Good luck,

Pitotman

[Pilot DAR]

Hello Cool Banana,

The DHC-6 300 has a standard MTOW of 12,500 as you know. A part of the reasoning for this, is that weight is the threshold between CAR3 and CAR4 for certification requirements, and there was a desire to keep the aircraft in a lighter weight category for several reasons. I have flown the Twin Otter at 15,500 pounds with ferry tanks, and I am aware that they have been flown at weights as high as 18,700 pounds. If you lost an engine at such weights, the other one would be taking you to the accident scene.

The Canadian military Twin Otters are permitted to operate at 14,500 pounds. I don't know how often it is done.

The factor which is not so well known is that it is a stated requirement that operations of the Twin Otter in a low altitude (rough air) role, or at higher weights, requires the operator to consult deHavilland for an analysis of the affect on the airframe. Twin Otter wings are subject to a life limit in hours and cycles, and any added stress upon them is greatly disliked. The life limit for that aircraft's wings could be reduced, which is very undesirable.

Yes, Transport Canada can issue flight authority at higher weights if they choose. This would be the case for any aircraft (I did it on a Cessna T207A). This authority will take the form of a Flight Permit, which would take the place of the aircraft's C of A for that flying. It is up to the applicant to demonstrate that the flight can be conducted safely, and recommend any appropriate restrictions to the flying. As such flight authorities are specifically issued to the aircraft, and most likely calendar time limited, you will not find any reference to them on websites.

Operation at higher weights is really hard on tires, and the rubber pucks which provide the suspension.

I hope this helps,

Pilot DAR

[V1... Ooops]

I been told that in Canada the DHC6-300 is approved to operate MTOW in the aerial work category is 14,400lbs?

This is most definitely not correct. The MTOW of the DHC-6-300 series is 12,500 pounds. Period, end of story. There is no jurisdiction in the world that has granted approval for civil operations above that weight, simply because de Havilland had a strict policy of not entertaining any requests for operations above that weight from civil operators.

It may be possible to apply for an exemption from the appropriate regulatory agencies (e.g. state of registry and states overflown) for the purpose of ferry flights. Such exemptions are typically granted on a one-off basis for intercontinental positioning (ferry) flights only when no other alternative route exists. Note that if the aircraft is equipped with wing tanks, these wing tanks must be full at all times when the weight is over 12,500 lbs in order to keep wing bending moments within the allowable range.

de Havilland constructed some DHC-6-300 aircraft with an engineering order embodied that supported operations at 14,500 pounds... however, these aircraft were sold to non-civil operators (for example, various military customers, including the Canadian Military), and military organizations can do what they want to with any aircraft because they are not governed by civil air regulations. Furthermore, wing life limits were considerably reduced from the normal 33,000 hours when operations were conducted above 12,500 lbs.

In Ontario, Canada, DHC-6-300 aircraft on amphibious floats operated by the provincial government are authorized to operate at takeoff weights of up to 15,000 pounds for the purpose of water-bombing forest fires. These aircraft have been modified by engineering orders to cope with the additional weight, and amongst other things, have thicker wing skins between the nacelle and wing root. If an engine fails, the first thing that the pilot does is press the button on the control column to dump the water load - and 4 seconds later, he or she is now flying a 9,500 pound Twin Otter, not a 15,000 pound Twin Otter.