Air Ministry Type P Relays - what No. is C256K?

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Member for

7 years 6 months

Posts: 145

Does anyone know what a C256K Type P relay is?

It looks just like an AM Type P relay, but that doesn't tell me enough. See snapshot.

On the bottom of this Vampire junction box: Type Q on the left; 5C/1722 Type P No. 1, 24 V in the centre; and C256K Type P on the right.

I guess C256K is the manufacturer's part-number. Maybe civil equivalent to AM parts. No idea what manufacturer. It doesn't look like Rotax or Dowty to me and they are the only ones I have any idea about.

I need to figure if it is Type P No.1 or No.2 or something else. Can probably narrow it down by test, but I don't know enough about these things at the moment.

The photo is of a junction box from Rhodesia, but I also have these as NOS from Australian sources.

Thanks.

Relay

Original post

Member for

13 years 11 months

Posts: 329

5C/1722, has the Rotax P/N of F.1504-1.

Type P relays are described as being single pole, rated at 20A.

For 5C/1722, it is a 24V, type P1 relay.

Type P1 being normally open and the type P2 being normally closed.

Nominal coil resistance for 24V operation is 255-285 ohms and 54-68 ohms for 12V operation.

Profile picture for user Nicko

Member for

7 years 6 months

Posts: 145

Thanks for the details aircraftclocks.

The No.2 is AM ident no. 5C/3181.

I suspect that we will find that the C256K is a No.2. The relay is in the Camera Gun circuit and the diagram from 1955 shows a Type P No.2 in the circuit, but the aircraft and this junction box has had so many mods since then, we don't really know where it is at. I'm working on drawing it up as best I can to help unravel its status.

Cheers.

Member for

13 years 11 months

Posts: 329

The Rotax part number for 5C/3181 is F.1503-1. A 24V, type P2.

Profile picture for user radarsdesk

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13 years 5 months

Posts: 207

Hi Nicko, e-mail has been sent to you, regards Dave