Are there any ex Shack people out there who remember testing the Petrol driven heaters?Worked ona ram air principle and had a combustion chamber into which petrol was sprayed and ignited and the heat generated was transfered to an outer chamber to heat and distribute the warm air around the cabin .There where two if I remember correctly ,one in the galley and one in the nose and starting them while airborne was an experience.So how much thrust was generated by them?!!!OK tongue in cheek stuff!!I hope they do get one flying ,I will try to be there for the occasion!

In a word, yes.

Your description of the Dragonair combustion heater is spot on. The Dragonair air-to-air heat exchanger heater (model number forgotten in the mist of time) was a very efficient item. It used approximately two gallons of Avgas per hour to generate 100,000 BTU of heat per hour (IIRC). The heater fuel supply was drawn from the aircraft’s main fuel system. There were two spark plugs, each with two earth electrodes. Unfortunately, someone who obviously had never worked on aircraft, designed the heater to be installed with one spark plug at the top and one at the bottom. Needless to say, after a couple of minutes taxying, the debris / stones / leaves etc blown back by the eight props and ingested into the intakes, made their way straight to the bottom plug (the effects of gravity, old boy). Most, but not all, heater starting problems were as a result of this mind-blowing design feature. The spark plugs were energised by a torch ignition system (vibrator booster coils), and only fired during the start cycle. Once running, the heater was self-sustaining (like a blow-torch). The hot exhaust gases were tapped to exit around the heater intake lip, acting as intake anti-icing. No thrust benifits to talk of from this arangement. Access to the heaters was, at best, limited. On the AEW II, the #2 and #4 heaters could be partially accessed from the ASV well as the ASV radar installed on the MR2 was removed as part of the AEW II mod. Still wasn’t easy though. Access to #3 was a nightmare.

The MR2 Phase 3 had four of these heaters fitted as follows (warning – details subject to passage-of-time errors):

#1 in the nose, fed the cockpit area and the nose section
#2 on the port rear side, fed the port fuselage and bomb bay
#3 in the rear fuselage, fed the rear fuselage area
#4 on the starboard side, fed the starboard fuselage and bomb bay

#2 incorporated a fan for ground use

When the MR2 Phase 3’s were converted into AEW II’s, the #1 heater was removed to free up space for the AN/APS 20 radar tray mounted in the forward bomb bay roof area, and to reduce nose weight (the same reason the Low Volts Power Pack was mounted behind the galley). The ducting from the #2 and #4 heaters were modified by closing off bomb bay feeds and extended to feed the cockpit and nose areas.

Why heat the bomb bay on the MR2? Because the torpedo’s carried required cossiting. There, there.

The heater ram intakes for the #2, 3 and 4 heaters were the stainless steel tubes mounted on the fuselage exterior sides behind the bomb bay. The portside #2heater intake was smaller than the starboard intake. Starboard fed #3 and #4. We used to have an adaptor made up to fit to a cabin conditioning trolley to allow ground testing of the #3 and #4 heaters. These intakes burnt all hands, clothes etc that came into contact while heaters were running.

On occasions, the combustion chambers would burn through, slowly filling the cabin with exhaust fumes. A very dangerous situation as the carbon monoxide was not human friendly.

Often, during start, there would be very loud bangs, pops and other, non-engineering type noises that always seemed to be the percurser of doom. Even after all the noises of complaint, the heaters would generally work, and pulse rates would drop back to normal.

Trying to get the heaters to light above 8000 ft was generally considered to be a bit of a challange. More than once, a “sumpy” would lift floor panels and tweek / adjust / swear until the heater would resign itself to work, bringing much needed relief to the frost-bitten crew, flying around in ‘racetrack’ circuits over the North Sea during the bitter winter months.

The heaters were controlled by FCU’s, or Fuel Control Units. These cylinderical units, approximately 10 inches in diameter and about 10 inches long contained three electrically operated solonoids mounted on a manifold ‘tree’. One solonoid was the main fuel on/off. One was the ‘Half-heat’ solonoid. The third was the ‘Full-heat’ solonoid. In January, ‘half-heat’ was never enough.

In the late ’80’s, we were suffering badly from the effects of both the RAF-wide moritorium on everything, and the run-down of Shackleton fleet support. On more than one occasion, I had to requesition from stores unserviceable heater FCU’s. The only reason for this was to canabilise in order to make serviceable units.

The big problem with this was, this was completely against RAF regulations and could easily have led to Court Martial, as we did not have the overhaul manuals, test equipment, or approvals for the maintenance of the FCU’s.

However, the RAF were the ones who didn’t renew the contract for FCU overhaul with civvy street. So, once again I stuck my neck out. I briefed my Chief on what I intended to do, and then proceeded to lock myself in tool stores for an hour or so at a time.

A couple of hours later, voila, serviceable heaters keeping Her Majesty’s Finest aircrew comfortable, enabling them to protect our shores at full efficiency.

Of course, doing ‘in-house’ repairs that wern’t legal meant that no paperwork was raised.

Instant COURT MARTIAL.

SENGO was unofficially briefed in advance, and unofficially supported the ‘make-do-and-mend’ self-sufficiency method, which extended far further than just heater FCU’s. But that, as they say, is another story.

Next time you are flying around in a Piper Seneca, Cessna 421 or similar ‘modern’ piston twin, think twice before you put the heater on. These aircraft use exactly the same type of heating system (remember, think blow-torch!!).

After all, are you really comfortable with the idea of starting a fire on board your aircraft, and then keep feeding it with high octane fuel??

Postfade,

Can’t find a mention of the Phase 3 modifications in your list.

P.S. the ‘racetrack’ mentioned above was the standard AEW II operating pattern and led to the naming of eight Squadron as the “Magic Roundabout” Squadron, each of the aircraft carrying an image of one of the Magic Roundabout characters.

camlobe