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Old 2nd Nov 2020, 10:41
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Beez51
 
Join Date: Aug 2007
Location: Sydney
Posts: 18
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Centaurus,
Thanks very much for your information. I very much enjoy your wise input and the style with which you deliver it.

Green.Dot, I have never conducted a three engine take-off for real, only in the simulator. l have however conducted many windmill taxi starts in the legacy C130 which I believe may have some similarities to the Viscount. The windmill taxi start for a C130 is more difficult from a controllability perspective than a three engine take-off. The procedure is usually conducted when an engine starter is U/S. Basically the engine to be started has it's prop blade moved out of feather to approximately 50 degrees blade angle or 'cuffed' The aircraft is then accelerated down the runway using the available engines and at approximately 90K the engine windmills up and being a single shaft engine, fuel and ignition occurs and hopefully it starts as the aircraft is safely aborted. The increased drag from the windmilling propeller makes it more of a handful from a control perspective than the three engine takeoff with a feathered propeller.

The golden rule for a C130 windmill taxi start is 'don't get airborne'. A USAF C130 whilst attempted one suffered a runway departure and got airborne. Fortunately, apart from hitting some approach lighting they lived to tell the tale.

The main issue is the non linear relationship between throttle movement and engine horsepower/torque. We used to demonstrate this right at the start by getting the student to push up the two symmetrical engines and note the affect. Initially there was a dead space and towards the top end of movement the throttles were very sensitive. I suspect that the RR Dart would be pretty awful in this area. We also set full nose down trim and pushed the yoke forward. We used to demonstrate the windmill taxi start with No.1 engine since it was the critical engine. We would get Bloggs to set the inboards to takeoff power and then push up No.4 until it was out of the dead area. You could hear the prop start to govern. We would brief Bloggs to put in almost full right rudder and hold only light nosewheel steering pressure. The idea was that when the airflow over the rudder started to yaw the aircraft to the right, No.4 was pushed up to counter this and keep the aircraft straight. At about 90K you would push the engine up to match the other two. The abort criteria was 100K or 4,000ft to run. The technique briefed was to abort slowly. This firstly, enabled the engine time above 90K which keep it accelerating and secondly, meant that the instructor had time to recognise if Bloggs hadn't taken the rudder out. No NWS in the right hand seat for the instructor. If the engine was going to 'hang' it happened as you were working hard and busy trying to stop.

As with most things there was lots that Bloggs could get wrong. Inadvertently jabbing the brakes whilst trying to keep straight usually killed off the acceleration and meant you where aborting with not enough speed to start the engine. Over controlling on nose wheel steering could be problematic. Our Kiwi mates had someone wind in almost full nose wheel steering at 100K. Luckily it just smoked and grenaded both nose wheels and damaged the nosewheel assembly. The momentum kept it going straight. The most common fault if someone was not adequately instructed was not getting No.4 out of the dead range and as they rolled down the runway they drifted right and then pushed the throttle up quicker. The result was that at ~60K the engine bit and the aircraft yawed quickly to the left. This is possibly what happen to the Viscount crew.

All RAAF C130 crews were trained and authorised to conduct three engine takeoffs out of Phnom Penh in Cambodia during operations in 1993 rather than leave an aircraft requiring an engine change. Luckily it wasn't required.

From a handling point of view the C130 three engine takeoff is easier than the windmill taxi start. The C130J on the other hand is a dream. Firstly, it for most weights can takeoff just on the symmetrical engines. With it's Automatic Thrust Control System (ATCS) the stretched aircraft limits the outboard engine to 60% thrust at 70K ramping up to takeoff power at 140K. This results in pretty much a constant foot load throughout. Have to respect progress!

RIP to an experienced crew on the Viscount.
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