Number for the Twin Otter

[larshgf]

Hi,

I need some number for the DHC-6 Twin Otter (300). That is speed, torque, flapsettings in climb, cruise, descend, approach and landing.
Can somebody help me with that?

Best Regards

Lars - DK

[Exaviator]

It's about 35 years since I last flew a Twin Otter but the following figures may be of some help.

T/Off @ Max Weight - MSL - ISA Conditions

Flaps 10 Lift Off @ 70 Kts (1.05vs)

Landing @ MLW - MSL - ISA

Flaps 37 degrees Speed at 50 ft = 84 Kts (1.5 vs)
Speed at Touch Down 64 Kts (1.15vs)

Climb @ Max Weight/Max Climb Power

Below 10,000ft = 92 Kts Above 10,000 ft = 85 Kts

Cruise @ Max Weight @ LRC 5000 ft ASL & ISA

RPM 75% Torque 33 PSI = 125 Kts IAS/140 Kts TAS

Cruise @ Max Weight @ Max Cruise Power 5000 ft ASL & ISA

RPM 75% Torque 50 PSI = 148 IAS/163 TAS

Needless to say there is a who range of power settings and speeds for each configuration depending on weight, altitude and temperature. You will need to consult the aircraft manual.

I flew the aircraft in the high and hot conditions of New Guinea, both in STOL and normal configurations and the frozen conditions found during the Northern Canadian winters. It proved to be an excellent aircraft to operate in both of these demanding environments.

Cheers Exaviator.:ok:

[larshgf]

Thank you Exaviator. I'll try these numbers! Interesting to hear that you have been flying this aircraft in these two extreme conditions!

Best Regards
Lars

[V1... Ooops]

Uh, I don't know how to say this politely, but the numbers posted above by Exaviator are not in agreement with the numbers I use - and I am the guy who writes the Twin Otter AFM!

The Twin Otter has been certified to many different standards - first to CAR 3, then later to SFAR 23, then to the BCARs (British standards in the 1970s, prior to JAR OPS-1), then to Australian DCA regulations (prior to publication of AFM amendment 19 in 2002). Exaviator indicated that he flew in PNG in the distant past, it is possible that he has quoted speeds, configurations, and power settings that were applicable to the Series 320 (Australian) variant aircraft prior to the publication of AFM amendment 19 in 2002.

FWIW, I've just finished writing an AFM supplement entitled "Performance to FAR 25 Standards" that will be published later this summer for operators who wish to conform to JAA 'Performance A' standards, and for Canadian and American operators who will be obliged to comply with the '2010 Rule' when it comes into effect next year. That will add yet another variable to what is out there...

Here are the current numbers for SFAR 23 certification standards. These are applicable to the Series 300 and variant standard landplane aircraft at the maximum weights permitted (12,500 lbs MTOW, 12,300 lbs MLW).

Takeoff - Flaps 10°, V1 73 KIAS, V2 80 KIAS, maintain V2 to 400 feet AGL minimum.

Initial Climb - following flap retraction, Vy is 100 KIAS, a higher speed may be used at the discretion of the pilot.

Initial Approach - no less than 94 KIAS if flaps are up, or no less than 85 KIAS with flaps extended to 10°.

Landing - Flaps 20°, Vref 80 KIAS or Flaps 37.5° Vref 74 KIAS

Cruise power is at the discretion of the pilot. At temperatures up to ISA +6° at sea level, 50 PSI torque can be used for cruise. This is not a common practice, because setting maximum cruise power results in a significant increase in fuel burn but an insignificant increase in speed. Many operators use about 480 SHP per engine for cruise, this can be achieved with a torque setting of 45 PSI and a propeller speed of 75% Np. At this power setting, fuel burn is approximately 300 pounds per hour (per engine), and a reasonable compromise between fuel burn and cruise speed is achieved.

Some other useful speeds, again, at maximum weight for the phase of flight, all in KIAS:

Best Rate of Climb 100 KIAS with flaps up

Best Angle of Climb 87 KIAS with flaps up

Best Single Engine Rate of Climb 80 KIAS with flaps 10°

Engine Failure after Take-off 80 KIAS, Flaps 10°

Enroute Descent Flaps up, speed limited by Vmo

Minimum Control Speed, One Engine Inoperative 64 KIAS. Vmc is always given in the take-off configuration, thus, flaps 10° is assumed.

Stall speed, landing configuration (Flaps 37.5°) - 56 KIAS

Stall speed, take-off configuration (Flaps 10°) - 66 KIAS

Stall speed, flaps up 73 KIAS

Manoeuvring Speed 132 KIAS from sea level to 18,000 feet. Limited by Maximum Operating Speed above 18,000 feet.

Glide Speed (both propellers feathered) for best range - 100 KIAS

Glide Speed (both propellers feathered) for best endurance - 77 KIAS

Maximum Operating Speed 166 KIAS for aircraft SN 271 and higher in landplane configuration, or earlier aircraft that are post Mod 6/1291 in landplane configuration. 156 KIAS for all other aircraft. Vmo begins to decrement above 6,700 feet pressure altitude, but this normally does not present an operational restriction.

Flaps Extended Speed Maximum 103 KIAS for flap extension up to and including 10°, maximum 93 KIAS for flap extension beyond 10°, both speeds quoted are for post Mod 6/1395 aircraft. Mod 6/1395 cut in at SN 290 and can be retrofitted to earlier production aircraft.

Hope this information is useful. If you happen to get out to Vancouver Island, drop in and visit - Twin Otters are back in production again.

[Exaviator]

"It's about 35 years since I last flew a Twin Otter"

You are quite correct the figures that I quoted were the certification figures in accordance with U.S. CAR Part 3 dated May 15th 1956 including amendments 3 - 8. which were applicable at that time.

That is why I also added the following advice: "You will need to consult the aircraft manual."

There is nothing like being up to date:ok:

[V1... Ooops]

Hi Exaviator:

On further reflection, I think it is possible that the numbers you posted may be applicable to a Series 100 or Series 200 (or variant) aircraft - these being the very early production aircraft that were equipped with the PT6A-20 engines, and had a MTOW of 11,569 lbs.

The numbers I have given are applicable to the Series 300 and variant aircraft, which encompass SN 231 to 844 inclusive.

Michael

[Exaviator]

Hi Michael,

Whilst I flew all three series of the aircraft the numbers come from the following manual:

Twin Otter - Series 300
Performance Data
Landplane Issue #8

Engines PT6A-27

Produced by The De Havilland Aircraft of Canada Ltd.
Downsview Ontario.
Published February 1972

Figures for the floatplane and/or later engines would be different.
Cheers :hmm:

[Complex]

Hi there V1... Ooops,

I've seen your comment where you talk about the AFM supplement "Performance to FAR 25 Standards" and the "2010 Rule", and can you say how much will the actual takeoff and landing performance values change?

Best regards.

[V1... Ooops]

The actual performance of the aircraft (its path through the air) does not change substantially, the difference is that in the forthcoming supplement, the performance calculations are done in accordance with FAR 23 Commuter Category specifications, rather than IAW SFAR 23 specifications. Additional information concerning operations from contaminated runways will be provided.

It is anticipated that the supplement will be published and available towards the end of Q1 2010.

Michael

[411A]

The Twin Otter is what it is, a 'heavy' under 12,500 pound general aviation airplane.
I operated the first one on the west coast of the USA in 1966, a -100 series model.
A nice airplane, no doubt about that, but still....not a transport category machine.
SFAR23/commuter category, notwithstanding....just a perfectly safe larger 'small' airplane.
I think the FAA went way overboard on the commuter category nonsense with the DHC-6.

[500 above]

Hi

Im sat in LSZR right now and there are several of the beasts in the AA hangars and two outside. These machines just dont die!

Oh and 411A, nice to see a post without the TriStar in it from you! ;)

[Complex]

Thank you for your answer Michael,

You say that there won’t be substantial performance changes, but there are significant differences between the requirements of the FAR23/CAR 3 normal category and the ones of the FAR23 commuter, and this should affect significantly (limit) the takeoff and landing performances, in my own opinion. Since you’ll be forced to consider the worst case scenario of OEI, you’ll have to provide a accelerate/stop distance (not demanded on normal category nor in SFAR 23), there will be brake energy limits imposed, just to mention some of the requirements not demanded in the previous certifications and that could probably further affect the DHC-6 performances…no?

Best regards

[V1... Ooops]

I'm in LSZR right now and there are several of the beasts in the AA hangars and two outside. These machines just don't die!

There's a picture of the flight compartment and new Honeywell Primus Apex® avionics suite of the Series 400 Twin Otter at this URL: Viking Air - 10/19/2009 - Viking in the Final Phase Of Certification Effort While Adding to Twin Otter Series 400 Order Book (http://www.vikingair.com/content.aspx?id=2051).

Double-click on the small thumbnail pictures and they will expand to about 2,000 pixels wide (very high resolution).

[Desert185]

Glide Speed (both propellers feathered) for best range - 100 KIAS

Glide Speed (both propellers feathered) for best endurance - 77 KIAS



I've been to Initial and Recurrent at Flight Safety, Toronto and have never seen Glide Speed for both engines out...although I could have used them for the last recurrent. :ok:

Not doubting the info, as your posting on the airplane was correct, but where are these officially posted? The AFM?

[Complex]

Hi there Michael,

do you have any idea of when the performance data according to the FAR23 commuter regulations will be available?
Because I've always seem to find always the same performance values, that I believe not to be the new ones...
And I'm doing a university study in cooperation with a company that operates in a short runway, and i would like to understand in what extent will the compliance with FAR 23 commuter afect a potential DHC-6 operation...

Thanks :O

[V1... Ooops]

...Not doubting the info, as your posting on the airplane was correct, but where are these officially posted? The AFM?

These two figures will be included in the upcoming revision of the AFM, which will be published later this year.

[V1... Ooops]

...do you have any idea of when the performance data according to the FAR23 commuter regulations will be available?

See my post above, dated January 18th 2010.