View Full Version : 1940s/1950s Heater Problems Causing Crashes

23rd Dec 2008, 11:01
I seem to recall reading somewhere of at least one air crash in the 1940s/1950s that was caused by a faulty cabin heater of rather crude design on board an airliner (DC4 or DC6). I can't remember where I read about it and wondered if anyone on the site can make sense of my raddled memory!

Any help much appreciated.

23rd Dec 2008, 11:50
Oct 24, 1947 In-flight fire caused the crash of a United Air Lines DC-6 at Bryce Canyon, Utah, with the loss of all 52 persons aboard. On Nov 11, another in-flight fire caused an American Airlines DC-6 to make an emergency landing at Gallup, N.M. Immediately following this second incident, the three airlines using DC-6 aircraft voluntarily withdrew them from service. The CAB determined that the fires had been caused by fuel leaking into the cabin heater system through an air intake scoop. After the problem had been remedied, the DC-6 returned to service in Mar 1948.

Medicine Bow Peak, Centennial, Wyoming,1955. DC-4.


Possible incapacitation of crew by carbon monoxide emanating from a faulty cabin heater was speculated upon based on recovery crew observations that crew bodies appeared 'discoloured'. This theory was never proven.

Actors - Ricky Nelson (http://listing-index.ebay.com/actors/Ricky_Nelson.html)

Ricky Nelson died in a DC3 crash in De Kalb, Texas in 1985. The crash was probably due to mechanical problems (including a faulty cabin heater).

An examination indicated the fire originated in the right hand side of the aft cabin area. The ignition and fuel sources could not be determined although many believe that the most likely cause was a defective cabin heater, a conclusion supported by records which showed that DC-3's in general, and this aircraft in particular, had a previous history of problems with the cabin heaters.

23rd Dec 2008, 13:08
Many thanks. I think it was the DC6 incidents that I was recollecting.

23rd Dec 2008, 13:30
Request for information in top slot:"... air crash in the 1940s/1950s ... cabin heater ... DC6 ..."
The two DC-6 fires in '47 followed the "Star of Lisbon" L-049 lessons in '46 -- these are the origins for safety systems used today. There is much tech' information on the DC-6 investigations. Two fleets, L049 & DC6, were "grounded" by regulator.

While the CAB investigators were working the UA608/24Oc47 fatal, the next case happened:

AA DC-6 / 11Nov47 SFO->Dallas ... inflight fire 1.5 hours after T/O (after 10am pst), landed safely at Gallup NM; big burned hole in aft-mid belly near gas Cabin Heater (ship had had magnesium Landing Flares removed earlier per CAB order). Just prior to fire, crew had transferred fuel between wing-tanks, and selected feed from alternate tank; Boost Pumps used in x-fer had been switched OFF....

... CAB investigators at Santa Monica were informed about AA's DC6 fire while it was still inflight. Accident a/c studied on ramp at Gallup: #4 Alternate Boost Pump set to HI, #3 Alt tank leaking fuel to ramp (and tank FULL), calculation of fuel used showed that 219 gallons were unaccounted (missing?); found unexplained fuel-stains on exterior belly skin leading to airscoop for Heater....

... AA event taught investigators: flares were discarded as a possible cause of initial fire on the UA aircraft. ... Post-accident AA testing: AA's mishap- pilot Glenn Brink role in flight test at Douglas, belly painted with Bon Ami fwd of Heater's Airscoop; test as in AA's accident flt Brink transferred fuel into #3 Alt Tank, fuel-overflow then exited via vent in fwd fuselage, fuel streamed-aft ten feet into air-scoop aft of wings into ducts and heater; CAB/Douglas did further test using dyed-water in #3&4 Alt Tanks (with fuselage painted with feldspar) to explore rivulet track on fuselage skin from #3 Tank-Vent to airscoop and into A/C-Heater compartment. Found that with #3 Alt Tank full and X-Feed OPEN with inflow to #3 Alt Tank, Boost Pump pressure forced fuel from Vent at 12.5 gpm -- that fuel would flow along exterior skin into scoop, and into Cabin Heater.... Modification relocated the vent.

Investigators focused on crew fuel-use procedures: AA accident pilots survived, and UA co-pilot described the accident captain's customary fuel-use method of Tank-to-Eng during CLB, then use of Alt Tanks at cruise, then tansfer-to-balance wing tanks; investigators found crews' fuel procedure was neither published nor forbidden (WWII flyers had long experience with unpublished but practical fuel transfer methods); pilots regarded fuel-transfer methods as subject to "pilot's judgement" or "Capt's discretion". Though Tank-to-Tank transfer was convenient on DC6, it was not deemed advisable -- CAB ordered crews to discontinue such fuel transfer methods.

CAB hearings, studied lapse in initial CAA certification flight test of DC6: fuel venting to scoop not tested? CAA admitted oversight of original flight test, didn't think fuel could reach AirScoop 10' distant.

CAB studied Fire Extinguishers: CAB tests on the AA ship found 60% of agent shot to "Boiler Room" escaped through compartment's air-outlet Vent (employed to vent fumes from Cabin Heater), Vent-adjustment controlled from cockpit, Vent should be Closed prior to Extinguisher discharge into "boiler room" compartment.

In '45 and again in '47 ALPA urged the elimination of Gasoline Heaters used in aircraft. On the DC-6 there were four such gasoline Heaters installed. Three Heaters supplied hot air for anti-ice systems: one heater located in the aft fuselage (near tail); one installed in left wing O/B of #2 Engine; and one heater in wing near #4 Engine. A fourth Heater installed in DC-6 fuselage mid section, near wing trailing edge: used to warm the ventilation air. These Gasoline Heaters required additional fuel lines throughout the aircraft.

DC-6 grounded for three month; on 7 Mar '48 fleet permitted to resume operation, service expected after two weeks. [CAB granted $3 million subsidy to UA and AA due to long DC6 grounding.]

Post-accident MODIFICATIONS to DC-6: Tank Vents relocated to near wing tips (to include flt test verification of trail of vented fuel-stream); Emergency Landing Flares relocated and insulated to prevent inadvertent firing; search for nonflammable hydraulic fluid.

In '48 Fire and smoke DETECTORS refitted, and Extinguisher Agents tested further: Between 1Jan48 and Jun48 twenty-two false fire warnings and 285 false smoke alarms reported by airlines. (Line experience with discharge of extinguisher agent, toxic gases seeped into cabin.)

In Jan48 continued mod-testing of DC-6 at Douglas, re-evaluate VENTILATION of aircraft after a discharge of CO2: parties (CAA and ALPA) observed that CO2 gas (discharged into below deck compartments ) lingered in cockpit, crew groggy. Mod: additional relief valve installed below floor by Mar'48. CAA and ALPA demanded smoke masks for crews. (See 13May48.) Precautions ordered prior to use of extinguishers (fumes) -- both for Constellation and DC-6; UA pilots told to don masks prior to discharge of below-deck agents.

23rd Dec 2008, 16:31
IGh has provided generally accurate information.
After the DC-6 inflight fires and subsequent investigations, the airplane flight manual was updated, and transfer of fuel between tanks was prohibited.

How do I know?
My Dad was the Engineering Project Manager at Douglas on the DC-6 and DC-7 programs.

The DC-6 (specifically, the DC-6B) turned out to be the most reliable and lowest operating cost 4-engine piston airliner ever produced, mainly due to its superb Pratt&Whitney R2800CB16 engines.

It was also a joy to fly, as I found out personally many years ago.

25th Dec 2008, 11:43
Can't remember the precise details but I think a 1950s UK airliner (Tudor, Hermes........????) crashed into a town (Southport ?) in the midlands killing a lot of people.
The investigation concluded the crew had all been poisoned by a carbon-monoxide leak from the flight-deck combustion heater.
I daresay someone will be able to come up with the full and accurate story ?

25th Dec 2008, 12:24
The ignition and fuel sources could not be determined although many believe that the most likely cause was a defective cabin heater, a conclusion supported by records which showed that DC-3's in general, and this aircraft in particular, had a previous history of problems with the cabin heaters.

I think it should be mentioned that combustion heaters(Southwind/Janitrol)were never a standard fit on DC3/C47 aircraft. The early versions used steam heating and later models utilised heat exchangers (hot air taken from a cover around the exhausts). A (non-UK) company I worked for several years operated a C47 with a Janitrol heater installed and it wasn't uncommon for the pilots to secure the airflow switch open so that the heater could be operated on the ground without cutting out due to overheating. They were rather blase about the risks involved. Quite frightening. I wonder how many operators didn't bother with combustion heater maintenance either.

An Argonaut crashed in Stockport in the 1960s but that was due to a fuel selection problem. I can't think of any UK airliner accidents caused by combustion heater leakage but I'm open to correction.

26th Dec 2008, 16:39
The steam heater on the DC-3 could be readily identified by the long exhaust stack, with a muff or jacket, on the R-1830 engines. I don't recall seeing this on R-1820-powered ships.

And the Stewart-Warner "Southwind" combustion heater was really popular in the VW - my 1964 Beetle had one.

26th Dec 2008, 17:15
Please excuse a complete amateur sticking his nose in but when a DC4 (?) crashed into Mt Canigou near Perpignan about 40 years ago, wasn't it suspected that crew errors caused by carbon monoxide poisoning from a faulty heater was the cause?

Sorry to be so vague, this is purely from memory.

26th Dec 2008, 18:00
Duckbutt: correct! As discussed on this very forum, in fact. Type 'Air Ferry DC-4 Crash 3 June 1967' in Search for further information! :ok:

26th Dec 2008, 19:53
You took your choice:

the exhaust muff heater created a potential avenue for CO migration into the cockpit if not properly maintained, or the combustion heater had the potential to create flames and/or explosion and/or CO distribution throughout, if not properly maintained.

Alternatively, you could just sit there, freezing in the cold and dark atmosphere and make some really dumb airmanship decisions while your simple mind was distracted by the -40 to -50C temperature.

The hazards were multiple and quite subtle, rarely the black and white perfection of 20/20 hind sight!

27th Dec 2008, 19:24
The cabin heater for the C54/DC-4 was in the overhead of the compartment just aft of the cockpit. It was the galley on some pax aircraft. The heater did not have a blower so only could be operated in flight when there was sufficient ram air to close a pressure switch and allow operation. This made it a pain for maintenance to check it out on the ground. Had a ground blower mounted on a cart with a tall mast and ducting that reached up to the top of the fuselage. You then attached a flexible duct to the inlet scoop on top of the fuselage and then could simulate flight.
Somewhat frightening though were the green stains on the cabin ceiling panels under the heater. 100 octane fuel was had green dye in it so you can make the connection. Also the couplings in the air ducting overhead often leaked and when flying through heavy rain the stewardesses would need rain coats in the galley.
There was a separate cockpit heater for the flight crew that did have a ground blower. You can see smudges from its exhaust on the port side of the nose of many DC-4.
Looking back I am amazed we had so few fires from cabin heaters with all the high test fuel piped around. The Connies had cabin heaters in the wing roots, the DC-6's cabin heater was in a boiler room in the lower fuselage.

28th Dec 2008, 10:58
There was a theory that faulty Cabin Heaters could have caused the loss of the British South American Airways Tudor 4's, Star Ariel and Star Tiger, in the Bermuda Triangle.

30th Dec 2008, 11:09
Carbon Monoxide contamination of the air supply through heaters seems to have been a feature of the times, as internal-combustion powered vehicles (road, rail, air) started to fit heaters. There were accidents on the railway in Britain with the new diesel locomotives in the 1960s for this reason of driver incapacitation, and older cars of the period, when heaters were still a chargeable extra (!) were also prone to it as well.

31st Dec 2008, 18:07
Muff type heaters where the engine exhaust heats the cabin air are fitted to a lot of light aircraft. They seem to prone to internal cracking at welds which lets the engine exhaust enter the cabin air supply. Not good!

In spite of the Carbon Monoxide threat from cabin heaters found on transport piston aircraft, the only CO detectors fitted I remember seeing were on the B377 Stratocruisers. I never saw any fitted on any DC-4/DC-6/DC-7's or any Constellation models L-049 thru L-1649.

7th Jan 2009, 22:01
Many thanks for everyone's answers on this.


8th Jan 2009, 10:58
I'm currently researching the disappearances of Star Tiger and Star Ariel of BSAAC, and would very much like to talk to captains and crew who had any experience of them on the Tudor 4's.

8th Jan 2009, 12:21
Yo might want to try and contact Richard Branson's mum, Eve Branson, who was cabin crew on BSAA Tudors.