Loss of AC = no flying controls?

[Fonsini]

I had always worked on the basis that a complete loss of main bus AC power was an inflight emergency due to the loss of instrumentation after the batteries give out, but after reading about the loss of a Vulcan B.1 when the flight controls seized I was left scratching my (obviously confused) noggin.

How would the loss of electrical power seize up hydraulic controls, or is this simply a case of the Vulcan using electrically actuated control surfaces?

Yes, I'm :\

[Exrigger]

Hi fonsini, the Vulcan had electro-hydraulic powered flying controls with each powered flying control unit being controlled electrically from the stick input via a mixer unit, what could be described as 'fly by wire'.

The electrical system being 200 volts, 400 hertz that provides the electrical power, with 8 elevon power units and a rudder unit the power comes via main busbar, which divide the power between the PFCUs.

If electrical power fails the PFCU lock valves prevent the control surface fluttering in flight, which would explain why a complete loss of power would mean no flying controls.

[BEagle]

Exrigger, whereas that it is true for the Vulcan B2, the B1 and B1A had totally different electrical systems. They also had ailerons and elevators rather than the elevons of the B2; however electro-hydraulic PFCUs were indeed fitted to all Vulcans.

The B1 and B1A had a basic 112v DC electrical system, with 4 x 24v batteries in series for back-up power; any AC needs were provided by inverters and transformers. There was also a low voltage 24v DC system with its own back-up battery. Whereas the B2 had a predominantly 200v 400Hz AC system, which was a vast improvement.

In the B2, if all 4 engines flamed out (e.g. after the shock front from a high level nuclear burst had been encountered), there was a RAT which would provide sufficient power at high levels to maintain flying controls whilst relighting was attempted; this was augmented by the 'Rover' AAPP at lower levels. The RAT/AAPP drill was a frequent training requirement and worked fine provided that no-one was stupid enough to allow an over-volting RAT onto the synch busbar. (Spilsby....??)

Although the B1 had the 4 x 24v 40Ah back-up battery system which was supposed to provide sufficient 'get it down' electrical power if the main electrical system failed, in the case to which Fonsini refers, the battery gave up long before it should have done.

[Exrigger]

Hi Beagle, thanks for the correction, I was working from memory with a bit from the aircrew manual and did not check what mark I took the gen from.

Along with the batteries there was also the APU and Ram Air Turbine (although this would occasionally fall off when deployed) that could of been used, but with no electrical power these probably would not have worked anyway.

[BEagle]

Did the B1/ B1A have a RAT? I thought that the RAT / AAPP were introduced with the AC system of the B2?

Also, I've never heard of a RAT 'falling off' - and the AAPP would be started by a cartridge in emergency rather than electrically. Although 'Valerie', a 35 Sqn AEO leader cocked things up on the ground and started the AAPP by cartridge, much to the Crew Chief's annoyance as he was surrounded by black smoke and sparks from the cartridge firing. Not to be outdone though, 'Valerie' managed to repeat the performance on a later occasion!

[Pontius Navigator]

In the Chicago crash, IIRC, the battery lasted 6 minutes. You could carry one battery in your hand they were that small.

I believe a RATT did indeed fall off a Scampton Vulcan :)

We once had a spectacular RATT malfunction. We were doing 350kts across the Libyan desert and there was a loud bang. The RATT did what it was supposed to do and slammed a lot of wiggly amps onto the bus before burning out. I think it also blew a few other circumstances circuits too.

Back at Akrotiri the crew chief 'fixed' the problem and we planned another sortie, fully fuelled, with the plan of dropping the RATT at TOC before commencing the sortie. Why j have no idea. RATT dropped and failed. 5 hrs fuel to burn off and t2t he chief apologised for not checking the fuses.

[The Oberon]

Beagle, you mention the Rover. As I remember it, the Rover was spoolled up before the intake scoop was fully deployed. In order to allow ignition before scoop deployment an oxygen bottle was used, always struck me as being a bit iffy.

[haltonapp]

The Vulcan had the same system of powered flying controls as the VC10. Mechanical input to a servo valve, which ported hydraulic fluid to one side or other of a piston to move a control surface. This hydraulic pressure was provided by an ac electric motor on each PFCU, no fly by wire until using an autopilot. The elevons used a suitable system of bell cranks a pulleys in a mixing box to convert the roll and pitch movement of the control column into a mechanical signal to the PFCU! This system was taught to me at Halton in the early sixties, before the VC10 came into service, so was not state of the art even then.

[ACW418]

The RAT fell off a Vulcan taking off at Cottesmore in late 1964 - I think it might have been Joe L'Estrange. It was in the early hours and normally I would have slept through any take off but because the noise was different - they aborted take off - I awoke and on enquiring what had gone on later found that the RAT had actually fallen off the aircraft but was dragged along by its cables.

We managed to turn our captains SD hat green. We were on QRA and were asked to do a compass swing. The AEO climbed aboard and turned on the batteries whereupon the AAPP cartridge started. Unfortunately the captain wearing his SD hat was just under the AAPP exhaust, was enveloped in a huge sheet of flame and the end result was a very cross green hatted captain. I seem to remember that the Crew Chief had a part to play in this as it was either him that turned the battery on or he had been doing something with the AAPP and had left it cocked for a cartridge start. The rest of us thought it very funny but were soon disabused of this!

ACW

[50+Ray]

While I agree with most of Beagle's comments about the dear old Vulcan, I think a possible slight on the Spilsby crew may have occurred. As I recollect the Board's initial report was all set to pillory the crew, and AEO in particular, after the crash, but after the digging and reconstruction they had to back off. The RAT in question was seriously over-volting. and arcing from poor insulation onto a previously pitted fuel pipe started a fire which was unstoppable. I seem to remember that in effect pulling the handle to deploy the RAT in this case started a chain of events which the crew could in no way prevent.
I only remember one instance of the RAT literally dropping off. I do recall a few which did not work as advertised, albeit rarely

[Rocket2]

50+RAY - I stand to be corrected but I recall the RAT cables had been incorrectly routed at the RAT end of the loom & over time chaffed the insulation to the point where the overvoltage caused a breakdown & short. My first days as a Vulcan phixer was spent checking the cable routing.

[Exrigger]

Thanks Haltonapp, I must of been asleep during that phase at Halton and in all my time working on the Vulcan I had always thought it was electrical signals that operated the PFCU,s, no wonder I did not get on as quick as I expected :{

Still it has got me reading the Airframe Course notes to re acquaint myself with all things Vulcan. :8

[haltonapp]

Ex-Rigger, I did my Vulcan course at Finningley in 69, and left "Waddo" in 1970, thankfully, had nothing further to do with the "flat iron" again, so have certainly not got any notes left to consult! But it was a great place to be in those days. The Raven Club was the place to be on a Saturday night for the young ladies of Lincoln. The Vulcan might have been a great aircraft for the two winged master race to fly, but I remember it was awful to maintain, I can still have nightmares remembering doing a wing fuel tank bag change in the middle of summer in a rubber suit with a breathing tube that hung out the tank panel. And as for that collection of ducting in the nose u/c bay with an alarming frequency of leaking hot air, what a design!

[Fonsini]

The level of technical knowledge hereabouts never ceases to amaze me, quite astounding.

Thanks guys.

[tucumseh]

The level of technical knowledge hereabouts never ceases to amaze me, quite astounding.

I agree. On my last aircraft programme (rotary) there were many complex design issues and unique design features, but by far the most impressive feat was Westland working out the load shedding convention in case of single or double generator failure. (Tough **** if all 3 went, but as all Mull of Kintyre watchers know helicopters can glide at will to any landing point:E). Mind bogglingly complex on an electrical system that was within 0.04kVA of max. They'd nothing to play with, complicated by (as beagle mentions) the usual requirement for a "get you home" mode. The Chief Designer's reply was typically robust. "Get you home?". You'll get a ###### parachute and be happy".

[NutLoose]

The VC10 PFCu's dragged a whole lot of wiggles when operating, IIRC the reason you used to hold a lot of the PFCU switches down when applying Ground power to the Ten was due to an early episode where the PFCU's on one aircraft remained online, so when external power was applied, the resulting loading resulted in the powerset rotating around itself.

[charliegolf]

Is there any truth in the story I once heard that, half way down the runway (waiting for the curvature of the earth to kick in, so they used to say), a Victor tanker crew realised the flying controls were not 'on'?

CG

[Rocket2]

"when applying Ground power to the Ten was due to an early episode where the PFCU's on one aircraft remained online, so when external power was applied, the resulting loading resulted in the powerset rotating around itself."

If you didn't do "pre 200 Volt" checks thoroughly on the Vulcan you ended up blowing all the bus bar fuses in the arse end when you put the power set on line - hell of a replacement job for the leckies. For all the crap jobs I still loved working on them :ok:

[lsh]

There was a VERY nasty electrical emergency on the Wessex, around '87 - '89.

IIRC the bare bones were:

Cliff Winching exercise on Antrim coast
Winchman and "survivor" on winch
GENerator caption
FRC drills = Faulty GEN "OFF"
So, quite correctly, they did select it "Off"

Then it all went BANANAS!
Rotor RPM fluctuating (with lift then loss of lift), associated Yaw, mega captions
They ran the a/c onto the field ahead, not easy when power is changing constantly & you also have two guy's underneath - who were deposited safely!

Please sit down whilst you read the next bit:
The Wessex had been in service over 25 years but there was no routine service schedule for the generators / brushes!!
I think the GEN was either "S" or "U/S" & some lasted a long time after fit, without an overhaul.

Consequently, when one GEN started failing, it dragged the good GEN down (Power balancing circuit, designed to share load by bringing lower GEN up!)
The good GEN produced a caption (dragged-down), and once the good GEN was switched-off.....
The bad GEN was producing low volts and messing-up the system.
Cannot quite recall why the engine computers did not freeze with low volts.
(Maybe they did / did'nt / did / did'nt etc?)

Nasty-Nasty!

That said, the Wessex was a MIGHTY beast, with lots of far-ahead technology, bear in mind it was a 1950's design.

lsh

:E

[Pontius Navigator]

Ish, interesting, IIRC that was the cause of the Vulcan Chicago crash, a cascade failure as a faulty component still on the bus caused each gennie to fail in turn.

Strange t o relate but my old man suffered that on a motor ship in the 50s.

[BEagle]

When BWoS built the VC10K, the load distribution was changed so that the HDU motor starting load back EMFs wouldn't upset the aircraft instruments. This meant that all attitude instruments were powered by the #1 and #3 busbars. In order to provide at least something in the event of an electrical fire on the normally-commoned #1 and #3 busbars, they included a '#3 Bus Tie Breaker Smoke Trip Switch', so that the offending source could be isolated. But any AC supply failure would normally be resolved by the system commoning the remaining supplies.

So it was theoretically impossible to have a #1 and #3 AC bus failure....wasn't it?

Riiiiiiiiiiiiiiigggggggghhhhhhhhht!

One fine day I was conducting an air test on 'The Lizard' which had just been retrieved from Scrapheap Challenge St. Athan in order to participate in one of Bliar's 'bring a bottle' Balkan wars. It had been left in open storage in the balmy Welsh climate for several months, until the gingers popped some engines back in, gave it a quick wash and brush up and invited me to come over and fly it.

All went well until it came to the shut-down and relight part of the test. After shutting down no. 3 engine, the system behaved as advertised - for a while. Then the #1 alternator decided it couldn't quite cope. But rather than come off line cleanly, the rust and corrosion in the alternator control panel refused to allow a normal disconnect. So various time delay units and bus tie breakers came out in sympathy to prevent a cascade failure and the next thing I knew was the bright red lights of the #1 and #3 busbar failure warnings, alert lights, lots of warning flags, failure of several PCUs and to add to the fun, the cabin pressure began to climb because whatever controlled it had now found itself without power. A few rude words followed from the Air Eng as he contemplated a panel full of warning lights which he'd never even seen in the simulator.

This was a bit of a bugger. My co-pilot advised ATC that we had a problem and wouldn't be able to change heading for a while, as every single gyro instrument was in the process of winding down....

The no.3 engine relit at the first attempt, so we soon recovered all the instruments and PCUs, regained control of the cabin pressure - and decided to call it a day.

In the case of multiple alternator failure, it would have been normal to drop the Electrical Ram Air Turbine. But it was just as well that we didn't, as when I took it up on the next air test, the conclusion of which required the ELRAT to be dropped, we had another exciting time as the ELRAT went well out of limits, shortly followed by a smoke warning. So we landed and evacuated with Trumpton in close attendance. The cause? Yet more corrosion, this time in an alternator rectifier which had turned green thanks to the lovely Welsh climate.....

So if an engineer claims it cannot happen, it very well might!

As a postscript, our wonderful Sqn Cdr was more concerned that I'd declined the offer of donating to the Med Centre's leech-handlers than the fact that we'd had such an entertaining day. Why had I declined? Well, we'd been sheltering by the fire wagons waiting for a crew bus for about 10 minutes and had probably ingested more crud from their thick black diesel exhaust than we could possibly have done in the aircraft on 100% oxygen.

[NutLoose]

I remember runs out on the apron adjacent to base when the recirc fan burnt out at max diff filling the cockpit with smoke, not just normal smoke but the nice stuff containing hydrogen cyanide :) the lads went on to 100% Oxy and told the outside guys to keep the fireman away from the door after declaring smoke up in the cockpit! fat chance! he was up the steps like sh*t off a shovel and was attempting to open the door at max diff! They got the quacks 100% oxy isn't good for you speech! but compared to hydrogen cyanide it was.

[Tengah Type]

CharlieGolf. Yes it really did happen. Fortunately with a 50 second plus
ground roll there was still time for the FCUs to spool up to pressure.
Otherwise the scenery around the Fido tanks would have been rearranged.