Sea King info needed
Thread Starter
Join Date: Oct 2000
Location: Little colonial airfield in the land of prawns, beer & roos
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
Sea King info needed
On another thread the following was posted about the good old Sea King
The reliability is not what it once was, and the change in the FRC's so as circuit breakers can now no longer be reset, for fear of it causing a fire, are, quite frankly, shocking.
Need any info on this restriction regarding circuit breakers, why when etc.
Any info gratefully accepted
H.P.
The reliability is not what it once was, and the change in the FRC's so as circuit breakers can now no longer be reset, for fear of it causing a fire, are, quite frankly, shocking.
Need any info on this restriction regarding circuit breakers, why when etc.
Any info gratefully accepted
H.P.
HP - with many SK emergency drills, the crew are invited by the FRCs to attempt one reset of a popped CB - this used to be the case in all situations but a new decree has limited the resetting of CBs where recovering the failed item/system is operationally essential only. I think they are acknowledging the age of the wiring looms in the older SKs but there is probably a healthy dose of a*se covering as well.
Thread Starter
Join Date: Oct 2000
Location: Little colonial airfield in the land of prawns, beer & roos
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
[email protected]
Well familiar with FRC's (wrote half of them myself!) After the reasoning behind the decision for possible action down here!!
New limits don't always make it south of the equator!
Well familiar with FRC's (wrote half of them myself!) After the reasoning behind the decision for possible action down here!!
New limits don't always make it south of the equator!
HP - following an investigation into a RN HC4 incident in which the MRGB Oil Temp Gauge appeared to fail, it was discovered that a number of other CBs had popped. During fault investigation the CBs were reset and power applied resulting in smoke and a burning smell in the cabin. Damage to the soundproofing was discovered where overheating of the wiring had occurred.
The CBs in the SK are current rated and require 0.35 to 0.8 seconds to operate, whilst arcing can occur for only 20 to 30 milliseconds, allowing cables to overheat and char with the associated risk of fire. Resetting CBs in circuits that have suffered short circuits or arcing damage may result in cables catching fire and affecting other circuits in the same cable loom.
Serviceable CBs tripped for trg are not subject to the same limitations.
That is a precis of our SD for the Mk3 and 3A, hope it sheds some light.
The CBs in the SK are current rated and require 0.35 to 0.8 seconds to operate, whilst arcing can occur for only 20 to 30 milliseconds, allowing cables to overheat and char with the associated risk of fire. Resetting CBs in circuits that have suffered short circuits or arcing damage may result in cables catching fire and affecting other circuits in the same cable loom.
Serviceable CBs tripped for trg are not subject to the same limitations.
That is a precis of our SD for the Mk3 and 3A, hope it sheds some light.
Join Date: Aug 2004
Location: over here
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
HP,
To add a little more to Crab's response:
The Mk 4 incident was found to involve Kapton wiring. Kapton is a very good insulator, and also very light, but is very susceptible to fire following arcing caused by damage. It was implicated in a number of accidents and incidents and has now been largely outlawed, but not completely. The SK airframes most at risk have been identified to the crews to help in the decision on whether or not to attempt a reset, but the problem is further compounded by the use of Kapton in lots of modification kits, hence the advice to aircrew covered all airframes and not just those with Kapton looming. If you are worried, then the manufactures will (should) be able to tell you how much Kapton was used in your airframes.
To add a little more to Crab's response:
The Mk 4 incident was found to involve Kapton wiring. Kapton is a very good insulator, and also very light, but is very susceptible to fire following arcing caused by damage. It was implicated in a number of accidents and incidents and has now been largely outlawed, but not completely. The SK airframes most at risk have been identified to the crews to help in the decision on whether or not to attempt a reset, but the problem is further compounded by the use of Kapton in lots of modification kits, hence the advice to aircrew covered all airframes and not just those with Kapton looming. If you are worried, then the manufactures will (should) be able to tell you how much Kapton was used in your airframes.
