Can any ex-Nimrod FEs answer this?

[Shaggy Sheep Driver]

Is it possible to get external electrical power onto the aeroplane when the two aircraft batteries are flat? We have an invertor powering our (obviously now grounded) MR2, but the procedure calls for battery power to be available before ground power will power the aircraft; no batteries, no power to the aeroplane.

This seems intuitivly to be wrong. Surely the aeroplane wasn't rendered unusable when it was in service if the batteries are inadvertantly allowed to get discharged? Is there a way to apply ground power without battery power being available, and then allow ground power to charge the batteries in the normal way?

Also, if the batteries are disconnected while ground power is powering the aeroplane, ground power is dropped and the electrics die. Did this happen with generator-supplied power as well? Would a Nimrod in flight, powered by the engine-driven generators, be rendered devoid of all electrical power despite it being available from the generators if the batteries failed?

CROSS POSTED ON TECH FORUM AS WELL

[SirPeterHardingsLovechild]

Generally speaking, there will be a DC relay to bring on the AC external power.

This can be shorted out for your purposes.

Your insurance will be invalidated

[Charlie Luncher]

May I suggest you put something in the title about fat chicks they are more likely to read it :eek:
Charlie sends

[SirPeterHardingsLovechild]

Fat chicks? Now I'm interested. But this is a Nimrod thread.

A Nimrod crew attend a Gay Pride re-union in Lesbos, and the accomodation manager requires 50 Euros to activate the Air Conditioning.

a) The Pilot pays the 50 Euros and moans about it all week
b) The Navigator moves in with the Pilot
c) The FE stays sweaty and moans about it the whole week
d) The Crew Chief hot wires his Air Con
e) The Co-Pilot moves in with the Crew Chief and it makes his hole weak

But seriously:-

For reasons that a FE will eventually tell you (once it has been explained to him by his Crew Chief), there will be a battery operated DC relay to apply external power. This is the 'clunk' when you select external AC. This can be fudged in the following circumstances:-

a) When you are being shot at. This is known as a Combat Repair Procedure
b) When your next stop attracts better accomodation and rates. This is known as an Operational Necessity (only applies to Nimrods & white fleet)
c) When there is a danger of missing last orders. This is known as a Dynamic Risk Assessment.
d) When the FE has left the emergency lights on overnight. This is known as a crate of beer for the lads.

If you still have the old batteries fitted, they should trickle charge after you have cheated the relay.

Of course, you might electricute yourself, or the batteries might explode, but what the hell.

SPHLC (Not an electrician)

[Top Bunk Tester]

SPHLC

With a lot of training you 'might' have made a half decent Air Eng, just a shame you'd have never managed to fit into the seat :}

[SirPeterHardingsLovechild]

f) The Ground Engineer hot wires his Air-Con, gets a 'Miscellaneous Expenditure' chit from the Co-Pilot, gets the Captain to sign it when he's pissed. Claims the money back on JPA and spends it on beer.

[kevnurse]

Flat batteries on a Nimrod render it a museum piece, which I guess is what it is. Without power to the Battery Busbar, which supplies the GPU switching circuit (for both AC and DC GPUs), the aircraft is dead and cannot be powered up. I suggest you disconnect both aircraft batteries, and get two 12V car batteries in series in to produce 24V and hot wire them to one pair of the now available battery terminations to power the battery busbar until you get the 200V GPU on line. Then you can reconnect the aircraft batteries and charge them up.

I suggest you disconnect the batteries every time you leave the ac for any significant time. There is one single unswitched lamp (sec jacks locked) that will be always be illuminated while the batteries remain connected and it will drain them in due course.

I once flattened the batteries while on det (refuel master switch, Doh!). Fortunately, it was a 2 ac det so we had 2 spares, not far away....

Kev

[fantom]

How come you've got a Nimrod anyway?

[MATELO]

How come you've got a Nimrod anyway?

Was just wondering that myself.

[woptb]

If you still have Ni-Cads fitted,be careful if you recharge them off A/C & if they get flattened on the A/C give the battery bay time to vent before connecting another set.The gas they give off on discharge is explosive,I lost a set of eyebrows learning that lesson!

[ANW]

XV231, the said aircraft is now resident at the Runway Visitor Park at Manchester Airport

exterior views here (http://www.edendale.co.uk/ANW/WFD.801.13.html). interior views are on Page 13A. Last delivery flight on Page 12

[PFMG]

Go on...what's written under the radar scratch pad?

[TheSmiter]

Go on...what's written under the radar scratch pad?Hopefully just the NSN for Scratchpad, Radar

Otherwise the good people of Manchester and t'North will eventually find out what spike is and who made up the AEO dream team.

And possibly discover that Flaunt was there as well as the luxury heads at Basrah International.

[davejb]

Fake!
According to the captions that's 231, but I've never seen a Nimrod as clean as that in my life! Muyst be more of that Hollywood CGI stuff....good grief, you can't even see a significant dip in the ESM seat cushion.

[Shaggy Sheep Driver]

It is 231, and she's in good hands. At least she is now that the guy who let the batteries get discharged has been hung from the refuelling probe!

Thanks Kevnurse - we always leave the batteries disconnected when power if not on the aeroplane, but if anyone 'gets their switches' wrong again and discharges the batteries while we have power on, that 'car battery' trick might be worth a try. Because we always disconnect the batteries, we leave the front off the battery compartment, so eye brows should be safe!

[OilCan]

Shaggy, to expand a little on Kevs.

Is it possible to get external electrical power onto the aeroplane when the two aircraft batteries are flat?

Nop. The GPU contactor is controlled by the Auxiary Control & Protection Unit (ACPU) which takes power direct from the Battery bus-bar, as does most of the contactors in the dc system. Note;this bus-bar is 'live' even with the batteries switched off (assuming there's any juice left of course) :8

Surely the aeroplane wasn't rendered unusable when it was in service if the batteries are inadvertantly allowed to get discharged?

Yep. We would reject the aircraft if the batteries continued to take a charge after 10 mins....unless we knew why or the fuzzy wuzzies were coming over the hill. Getting airborne with suspect batteries was bad ju ju.

Is there a way to apply ground power without battery power being available

Nop. Unless you've got another source of dc as Kev suggests. Either through the batteriy terminal connectors or jump leads direct onto the battery bus-bar, but you must disconnect the battery terminals first...
....but I never said that. :oh:

and then allow ground power to charge the batteries in the normal way?


:eek::eek::eek:BIG BIG CAUTION :eek::eek::eek: This is not the normal or the safe way to recharge NiCad batteries from flat. If your not aware please Google "NiCad Thermal Runaway"....I'd hate to see you blow the old girl apart!!!:sad:

if the batteries are disconnected while ground power is powering the aeroplane, ground power is dropped and the electrics die.

By 'disconnecting' I assume you mean pulling the battery terminal connector plugs, then yes; because you've removed the supply to the battery bus and the ACPU, the GPU contactor will drop out.
When powered by the generators the GPU contactor wasn't a player...unless the GPU contactor actually closed....but that's another story.

Would a Nimrod in flight, powered by the engine-driven generators, be rendered devoid of all electrical power despite it being available from the generators if the batteries failed?


No. Only the battery bus would be dead, which would take out the Engine Fire Extinguishers but not a lot else. Everything else on the A/c would remain powered.

In fact fail all generators and both batteries, the old girl was still perfectly flyable provided the pilots could see which way was 'Up'. There were many things that Mr de Havilland got right that would put a modern electric jet to shame.....but don't tell the holiday makers. ;)

Oilcan :cool:

oops posts crossed.

ps. Sounds like she's in good hands. :ok: ...but watch for the thermal runaway....once the temp and current flow starts to build it can be impossible to stop it till it goes BOOM. :eek:

Hope this helps.

Oilcan

[Vim_Fuego]

Fake!
According to the captions that's 231, but I've never seen a Nimrod as clean as that in my life! Muyst be more of that Hollywood CGI stuff....good grief, you can't even see a significant dip in the ESM seat cushion.

Agreed...she was never that tidy when I flew on her. This is the frame that famously had a scrape at St Mawgan with a crew on L1 or L2 IIRC.

[Shaggy Sheep Driver]

Thanks Oilcan, especially the tip about recharging flat Nicads. When it happened to us, we took the batteries to a specialist (at the Airport I think) to get them professionally re-charged.

What worries me a bit is that at some stage 231's Nicads will die through old age and no doubt replacements will be expensive and hard to source. I did wonder about replacing them with a stabilised +24Vdc mains-powered power supply. Obviously this would be of no use on a flying Nimrod, but might do the job for us on 231 now she's static. We'd take professional advice of course before even thinking of doing anything like that! Would hate to damage the old girl!

Cheers

Shaggy.

[Avionker]

Well those interior shots were interesting for me. I left the mob in '99 after 15 years, the last 7 of which were on ACO Flt in NST. What happened to the aco HCU's? And the CTS display is totally different, I was used to the big huge round thing.....

[OilCan]

When it happened to us, we took the batteries to a specialist (at the Airport I think) to get them professionally re-charged.



Very....very wise move.:ok:

The main attractions of NiCad was the physical size and voltage retention when under load, - not an issue now clearly, but the main down sides were maintenance costs and potential hazard. The hazard being reduced by regular quality (and no doubt expensive) maintenance. :ouch: In service IIRC they were changed every 28 days or so (I think???) and even unused on the shelf over that period you may see a 10-15% reduction in output. In short, regular maintenance is critical to both performance and safety.

Some form of mains supply would be ideal for the longer term, and I don't see why a set of Lead Acids wouldn't suffice as a standby in the near term, the difficulty will be deciding when to stop using the NiCads bearing in mind their potential for runaway will increase as they degrade.

"Professional advice"...again...wise move. :ok:

Oilcan

[Charlie Luncher]

See Shaggy one mention of Fat chix and you get a response, now if you want to keep them interested you need to add a Mars Bar:ok::E
Charlie sends

[OilCan]

Deep fried of course. ;)

Oilcan

[MFC_Fly]

Don't mention fat chix on a Nimrod thread!! There might be a certain Nav lurking around that somehow managed to find the only fat ugly 'chick' in Aalborg - although she was more of a whale, as the wet team reminded him every wet brief thereafter :ok: If you've ever been to Aalborg you'd know exactly how hard it is to find a chick that isn't a mega-babe there :sad:

[woptb]

Ni-Cads are VERY heavy, used at St Mawgan in our regular Nimrod Line Flight's strongest 'liney' contests; If you could walk to the back bays from the line carrying a pair, you could leave the monastery!