Dumb question regarding DHC-6

[Rowdy]

This might sound completly stupid to some but here goes anyways. I've worked around the Twin otters a bit but had never paid attention to this. What sort of de-ice equipment do they use? I don't specifically remember seeing boots, but maybe I was just too busy at the back cargo doors to see them. Are they even equipped with any kind of ice protection?

[Water off]

They have boots.

[ODA]

Some have boots some don't! Most have windshield and prop heat.

['79K20driver]

The only standard equipment is pitot heat. Boots are an option and so is prop and intake heat. There are also heated windscreens available as well.

[Rowdy]

Perfect! Thanks guys!

[oldtimer]

Don't remember if it still is this way but at one time you could not file and fly IFR in a floatplane so any Twotter used mostly on floats did not require anti-ice so many either never had boots installed or they were removed. Early Twotters had a rubber/electric engine intake boot but it was determined that it was not required so they were removed. The standard IFR equipped Twotter has pneumatic boots on the wings, horizontal stab and vertical fin, inertial seperators in the main engine air intake, oil to fuel heat exchangers, heated pitot and stall warning, electric heated windscreen on both pilot and co-pilot side and the static ports are in a non-iceing area. I forget what they used for fuel vents. usually it is heated and windshiel wipers.

[pushyboss]

The static ports use NACA anti-ice vanes as do the fuel vents. Early models of the DHC-6 also had an alcohol de-icing system for the windsceen but they were removed as the tank was considered a fire hazard. It also sat under the pilot's seat .

[Cat Driver]

We operated a fleet of them IFR on floats out of Vancouver harbour with Air West Airlines in the mid seventies and they only had heated windshields.

Of course we were restricted to no known icing....

Cat

[chubbee]

The windscreen wash system is still installed and used by some on the DHC-6. There is no mandatory requirement to remove it.
It is as problem free as the same system in your car and works like a charm on ice, bugs, dust, pollen, salt spray and etc...

[pushyboss]

Approximately 70 aircraft of the total production incorporated the deice/wash system. The final strw to the alcohol deice was the fire and crash of Pilgrim Flight #458 on February 21, 1982. The NTSB accident report # is NTSB-AAR-82-7. The cause of the crash ws determined to be the leaking of alcohol from the alcohol tank located underneath the captain's seat. As a result the NTSB recommended the removal or modification of the alcohol system (Class II Priority action A-82-56) on July 13, 1982. The FAA and Transport Canada adopted the recommendation and issued the following Air Worthiness Directive.

Most operators opted to remove the system completely, although the AD did not require it, but the AD did require that no alcohol could be used in the system due to it's flammable nature.
___________________________________________________________

Header Information
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
Amendment 39-4517; AD 82-26-06

Airworthiness Directives; DeHavilland Model DHC-6 Series Airplanes


Preamble Information
AGENCY: Federal Aviation Administration, DOT


DATES: Effective December 27, 1982.






Regulatory Information

82-26-06 DeHAVILLAND: Amendment 39-4517. Applies to Model DHC-6 (serial numbers 1 through 709, 711 through 735, 737 through 753, 755 through 761, 763 through 779, and 791) airplanes which incorporate a windscreen washer/deicing system certificated in any category.

COMPLIANCE: Required as indicated unless already accomplished.

To prevent leakage of isopropyl alcohol in the crew compartment and a possible crew compartment fire, accomplish the following:

(a) Within the next 25 hours time-in-service after the effective date of this AD, and each 200 hours time-in-service thereafter inspect the windscreen washer/deicing system for evidence of leaks in accordance with the Accomplishment Instructions of DeHavilland Service Bulletin S/B No. 6/422, Revision A dated June 18, 1982.

(1) Replace any defective components which could cause leaks and ensure that all tubing is secured in accordance with Accomplishment Instructions Step 3 and Step 6.

(b) On or before November 30, 1983:

(1) Install a permanent placard having letters of 1/8 inch minimum height on or near the washer/deicing fluid tank filler which states "DO NOT USE ISOPROPYL ALCOHOL OR ISOPROPYL ALCOHOL MIXTURES."

(2) Install a placard having letters of 1/8 inch minimum height adjacent to the windscreen washer/deicing system switch which states "WASHER ONLY" and operate the airplane in accordance with these placard limitations.

(3) On airplanes certificated for flight into icing conditions, install an electrically heated windscreen in accordance with DeHavilland Modification S.0.0. 6007, Issue 7 dated May 17, 1982.

(c) The inspections per paragraph (a) of this AD need not be accomplished when the placards required by paragraph (b) are installed.

(d) The airplane may be flown in accordance with Federal Aviation Regulation 21.197 to a location where this AD can be accomplished.

(e) An equivalent method of compliance with this AD may be used if approved by the Manager, New York Aircraft Certification Office, ANE-170, Federal Aviation Administration, 181 South Franklin Avenue, Room 202, Valley Stream, New York 11581, telephone: (516) 791-6680.

This amendment becomes effective on December 27, 1982.
d the following Airworthiness Directive on December 27, 1982.

_____________________________________________________________

[Rowdy]

So the tanks can only be used for bugwash essentially then.. Interesting.

How big is the weight penalty with the de-ice equip. installed? Boots, Intakes, heated windscreen and props?

[golden hawk]

The standard IFR equipped Twotter has pneumatic boots on the wings, horizontal stab and vertical fin

The vertical fin did not have a boot.

[kilpicki]

The alcohol tank is or was not under the pilots seat but to the left of it at floor level beside the outside skin.

A good place to put the first aid kit.

I thought it was manditory to remove them but thanks to the previous post we now know the facts.

I do know the wind screens come in 3 different variations, glass for the electric de ice and thin and thick plastic so be cautious when ordering a replacement.

[Dash 27]

I work for a company that operates Twotters IFR, and I've never heard of vertical stab de-ice boots.

[twotter]

There is nothing that will stop you from operating a twotter on floats IFR if it equiped and certified, or has there been in my memory.. If you don't have the de-ice equipment, well, you just don't operate it in ice. Just like any other airplane.. Of course your minimums will suck in most cases because they don't have many ILS's into water aerodromes but it can sure help enroute...

As Cat said, a while ago there used to be quite a few operating here on the coast, and recently Borek used to do it just a few years ago. West Coast has been looking at it for a while but the fuel requirements coupled with using 100 and 200 srs airplanes makes it a bit prohibitive.

If you add the de-ice equipment it will add at least a couple hundred pounds to your airplane with the boots, windshield, plumbing wiring timers etc. You would have to check the equipment list for the exact weights.. And as mentioned before, there is no boot for the vertical stab.

[chubbee]

On an aircraft with the belly full of fuel it would be a bit redundant to worry excessively about flammables that are 50% or more water (common windshield washer fluids).
Fuel vent manifolds "seeping" with a full fuel load is pretty common on the DHC-6.
What powers the fuel quantity indication on the twin? Oh yeah,26V AC from the inverter. Where are all those knarly old cracked/corroded fuel quantity wires? Right at the bottom where the fuel seeps collect under the belly panels.
However,with the washer tank and plumbing made of plastic filling it with a flammable fluid would be foolish as any damage or fire could compromise the fluid containment.

[twotter]

The fuel quantity system is actually powered by 28vdc until mod 6/1169 is incorporated into the airplane. It then comes from the 115vac bus.

[golden hawk]

This might sound completly stupid to some...

I don't think there is such a thing as a stupid question in this business; only stupid mistakes.

[Dash 27]

Cheers to that...

[Lost Lake]

De-Ice?... Shit I just wish for A/C and/or sun visors....