Caledonian Chipmunks



Author Topic: Replacement Starter Relay/Solenoid  (Read 354 times)

0 Members and 1 Guest are viewing this topic.

Offline WB650 Skylark

  • Posts: 37
  • Country: us
Replacement Starter Relay/Solenoid
« on: Friday August 10, 2018, 04:16:25 UTC »
I am planning to change out the starter relay/solenoid on my chipmunk which is fitted with the Type C.0225 24V 3-jaw starter motor. Looking through the parts list it shows two possibilities 5CW/4621 Relay, Type J and 5CW/6452 Relay, Type Q not sure which is the correct one for my starter and what the difference is.

Also wondering if I can just use an intermittent duty 24V starter solenoid such as SKY-TEC STS-S24 Starter Solenoid thinking a brand new unit is probably better than trying to find NOS of the origonal.
My aircraft is registered Experimental in the USA.

Appreciate any advice
Thanks,
WB650 Skylark

Offline Bob

  • Posts: 348
  • Country: 00
Re: Replacement Starter Relay/Solenoid
« Reply #1 on: Friday August 10, 2018, 22:08:27 UTC »
I think the SKY-TEC STS-S24 would work, I'll check our's tomorrow ( UK time ) and see what we have.

Offline WB650 Skylark

  • Posts: 37
  • Country: us
Re: Replacement Starter Relay/Solenoid
« Reply #2 on: Sunday August 12, 2018, 14:22:59 UTC »
I put the Sky Tec 24 V starter solenoid on along with a freshly overhauled (SIL Industries) Starter and new push switch and new switch circuit wiring connected to the 24V supply. The prior starter solenoid was activated through the switch to a ground, not the original circuit per the manual. Anyway happy ending (for now), everything works magnificently, I hope to finally get my intermittent starter issues behind me.
When SIL overhauled my starter they pointed out and replaced the LH nut that holds the dog on mine was badly worn, good advice to replace this from Dick Gower earlier.

My next project is replacing the rubber donuts in the main landing gear, a little apprehensive about starting this one

Thanks,
WB650 Skylark

Offline speedbird1

  • Posts: 549
  • Country: us
Re: Replacement Starter Relay/Solenoid
« Reply #3 on: Monday August 13, 2018, 04:18:32 UTC »
Hi Skylark,

Changing the donuts is not really difficult.  Just remember that the bottom end is held in by bronze plugs that are under a worm drive (Jubile??) clip and uses a 4ba thread inserted to pull them out.

The rest is just how much corrosion is holding it together and then make sure you shake the donuts up in a bag of graphite powder and remember the order the blocks and spacer discs have to go back??  The graphite will change your complexion!!!

To get the leg apart can be a challenge using suitable percussion instruments!! And even use of a deep freeze to shrink some of the parts, when her at home is not watching.

There is also an AD that requires a sample be taken from the top of the shiny part of the leg and analyzed to see what type of steel the shiny bit is made of. A cheap UK contractor made a lot of them of the wrong stuff that is too soft. You will not find anyone in the colony that has a clue what DTD numbers are.  Mine went to the UK.

Speedbird 1

Offline john henderson

  • Posts: 276
  • Country: gb
Re: Replacement Starter Relay/Solenoid
« Reply #4 on: Monday August 27, 2018, 11:37:55 UTC »
For the record, when the issue of substandard legs came up, an "unnamed" BAe engineer admitted to me that the legs in question were a batch manufactured by BAe for an overseas operator.  For some reason they were made to a different material specification.

The reason for the recall was that a senior RAF pilot flying a civilian chipmunk force-landed into a ploughed field and allegedly one of the legs buckled so that the aircraft turned over.  The CAA had things to say about this and so BAe issued the TNS in order to eliminate the alternative legs from the world's fleet. 

Its unclear how many legs actually got into service and how many may still be lying around.  Be that as it may, in normal use they are probably ok, and for all I know there may well be a number still flying.

The net result as you may be aware, is that we all had to remove our U/C legs, dismantle them and collect samples for analysis.  Even if you could show the legs were the original (as we could) they still required the samples.
john h

Offline Nigel Stevens

  • Moderator
  • Posts: 245
  • Country: fr
Re: Replacement Starter Relay/Solenoid
« Reply #5 on: Monday August 27, 2018, 16:40:42 UTC »
Hello John,  is there an approximate fabrication date?  Manufactured by BAe, implies it was not de Havilland.
best
Nigel

Offline Dick Gower

  • Posts: 302
  • Country: au
Re: Replacement Starter Relay/Solenoid
« Reply #6 on: Tuesday August 28, 2018, 05:14:06 UTC »
Back to the starter circuit Skylark: there is a serious safety issue if you adopt the automotive arrangement.
 
The original starter circuit is designed that way for a very good safety reason.  The 24V positive bus is switched to the solenoid during starting because, that way, a short circuit to the airframe can not result in un-commanded starter engagement.  On the ground this could be very serious but in flight probably catastrophic.

With the automotive arrangement which has bus power permanently on the solenoid, a short on any part of the starter wiring to both cockpits is going to engage the starter.
So, in summary, you really need any 28volt solenoid which has two coil terminals (not one terminal with the other end internally connected).  These are usually intermittently rated which is fine.

The type Q relay you mention is a small relay behind the front instrument panel and is part of the generator failure circuit and not applicable to the starter.
Dick Gower
Melbourne,
Australia.

Offline john henderson

  • Posts: 276
  • Country: gb
Re: Replacement Starter Relay/Solenoid
« Reply #7 on: Tuesday August 28, 2018, 09:10:15 UTC »
No Nigel, I did not get a date or even a decade.  But BAe took over de Havilland quite a long time ago.  my guess would be that actually BAe had them made by a parts sub contractor of which there were many.
john h

 

Copyright © Caledonian Chipmunks