View Full Version : Lightning T5 Starting System

12th Apr 2015, 22:22
The Lightning is a T5 variant, based at Cranfield, maintained by a team of volunteers and fast taxi run on various dates during the summer months. More info can be found at: lightningt5.com.

Lightning engines were originally started using an IPN monopropellant starter, but this is expensive, difficult to find and the group have replaced that with an electric starting system running at approx 160 volts DC. Presently, this is derived from 6 x 28v NiCad aircraft batteries, wired in series for starting and individually charged offline. The ongoing maintenance, uncertainty about charge state and ageing of the batteries has made it difficult to guarantee reliable starts. Another engineer designed the 160 volt starting panel, but has moved on. Iím new to the group, but have been asked to find a more robust long term solution. The group have a 25Kva Houchin GPU, which could be used to charge the batteries at start of day, between runs and augment the battery power during starting, but this requires some means of converting the 208v 400hz 3 ph output to a more suitable dc level.

I'm proposing a two track approach:

1) Buy in a 25 kVA 400Hz transformer and build a 160v dc transformer rectifier, in parallel with the batteries for starting and with constant current control when charging. I have two quotes for a suitable transformer thus far, but the price is not far short of astronomical.

2) Find 6 off surplus 208v 400Hz 3ph -> 28vdc, 200-300 amp transformer rectifier units (TRU's).

Tru's are a standard fitment on a variety of a/c and have a couple of smaller 50 and 125amp units in my own collection, but we really need higher output types and 6 of them, so we can allocate one per battery.

Background here is electronics and can build new or modify surplus kit, but not sure what has been used where and on what a/c. For example: What sort of TRU's / power systems were used in older (scrapped) commercial aircraft that might be pressed into service ?. Some RAF types used a 112v dc bus for the heavier loads and would assume that they used large tru's to generate that voltage, rather than dc generators. Perhaps the same for commerical a/c. To sum up, we're looking for large kVA 400Hz transformers, TRU's, or other high power a/c power systems that might be pressed into service. Ideally, this needs to be up and running by mid to end of May this year. Suggestions, ideas, sources etc would be appreciated...


16th Apr 2015, 21:45
Back in the 1980s the two Hunters at Hurn (G-HUNT and G-BOOM) had ex Comet electric start systems. IIRC these were 112v DC using 4 batteries in the gun pack with a rotary contactor to change them to parallel and charge them off the 28v bus.

16th Apr 2015, 22:22
To digress the Comet starter was 120vdc. For a start it required 28vdc and 120vdc. Normally provided by a GPU. Under extremes an internal start could be carried out. The Comet had six batteries (24v) and five of these were connected in series for a start. The remaining one being used for Ignition and fire protection. In the Comet installation the switch between series and parallel was done with a truly massive wafer switch cable operated from the Engineer's panel.
Some things you never forget.
A full battery change was needed after an internal start on return to base.

Art Smass
16th Apr 2015, 22:48
Might be worth you posting this request in the Military Aircrew forum - there are quite a few ex Lightning guys in there:ok:

India Four Two
16th Apr 2015, 23:59
Back in the 1980s the two Hunters at Hurn (G-HUNT and G-BOOM) had ex Comet electric start systems.

The Hunter at Tauranga (ZK-JIL) uses external compressed air bottles.

17th Apr 2015, 21:41
Super Puma L1 has 2x 115v 3 phase TRU's with a 28v 150 amp falling volts / load characteristic output, they are connected in parallel when dc bus bars are coupled. I think that Bristow 's are scrapping their L1 fleet perhaps they can help you out with surplus units. Hope this helps.

12th May 2015, 16:36
Bit late getting back this. Looks like the project temporarily on hold, no funds, but many thanks for all the replies.

I think the Comet starting system was the model for this conversion. They are having to run with 6 batteries due to the starter gear ratios, which dictate a higher starter motor speed.

The Hunter conversion looks particualrly interesting though, especially the bit about the changeover switch, which must have been real fun to wire up. When this project does go ahead, will probably build a constant current charger to charge all the batteries in series, running from the gpu...


15th May 2015, 08:24

The guy that did the installation on the Hunters at Hurn was Ivan Henderson. I don't know if he is still around but it might be worth trying to find him.

Cheers, Dixi.