Research on the BAC 1-11 electrical systems

[keskildi]

quite a unusual question, following a request received from a Djibouti friend, studying in a local technical college ....

this young lady (yes, they do work in mecanical and electrical matters as well) is preparing a ''memoire'' related to the electrical distribution system of a One Eleven .... why this peculiar aircraft, would you say ?

just because her country just bought one !

any ideas where I could , on her behalf, collect such info on the internet....

you help will be greatly appreciated

Keskildi alias Gerald

(Keskildi being the french QRI user's surname when talking .. english abroad, kind of ''SAY AGAIN'' or ''what the f**** is he saying '' hence my callsign )

[forget]

Try the guy on 'Contact Me' below. He may point you towards some spare manuals.

http://bac1-11jet.co.uk/bac1-11jet.co.uk%20Contents.htm

[Chris Scott]

Hi, Qu'est-ce-qu'il-dit,

Would be interested to know where Djibouti got their 1-11 from, and what model it is, if you have any info.

Regards,

'oo-eez-kolling

[keskildi]

It's probably a -500 (seating capacity above 100 announced) but I wonder if it's an aircraft of Romanian or original manufacture

I don't know the serial number or reg yet

I'll let you know, of course

info, (in french, I'm afraid) about this new equipment...

La compagnie aérienne Djibouti Airlines vient de renforcer sa flotte avec l'acquisition d'un nouvel avion de Type BAC-1-11 qui desservira les pays de la région. Vendredi dernier, la piste de l'Aéroport International de Djibouti accueillait un nouvel appareil aux couleurs de Djibouti Airlines. L'appareil, de type BAC-1-11 d'une capacité de 104 passagers a été réceptionné à son atterrissage par MM. Nabil Deyfallah et Salam Goubari respectivement Directeur général et directeur commercial et marketing de la compagnie Djibouti Airlines. Ce nouvel avion doté d'une capacité d'accueil de 104 passagers, desservira à partir de Djibouti les vols à destination du Yémen, Dubaï, Somalie et l'Ethiopie.

http://www.lanation.dj/news/2008/ln46/20080418790.jpg

Selon M. Salam Goubari, directeur commercial et marketing " par l'acquisition de ce nouvel appareil tout comme celle d'un autre programmé très prochainement, l'objectif de Djibouti Airlines est de renforcer ses capacités opérationnelles" précise t-il. Il s'agit aussi d'une exigence requise en matière de trafic aérien et pour se mettre en règle avec l'International Air Transport Association (IATA). Ce qui suppose que Djibouti Airlines doit mettre à niveau l'ensemble de ses appareils et de ses équipements. On se souvient qu'au mois de janvier dernier, Djibouti Airlines avait conclu à Sanaa un accord de partenariat avec la compagnie aérienne 'Yemenia'. En effet, dans le secteur du transport aérien, les seuls pavillons qui tirent leur épingle du jeu sont ceux qui ont su unir leurs forces pour défendre leurs intérêts ... ou qui en ont fait des partenaires plutôt que des concurrents. Djibouti Airlines semble retrouver des couleurs depuis son mariage réussi avec Yemenia

Pour preuve, les activités du transporteur local augurent déjà de nouvelles performances à la faveur de prestations de qualité répondant aux exigences les plus pointues. Cependant, pour s'adapter aux nouvelles exigences et faire face à une concurrence de plus en plus rude, il ne suffit pas de changer de logo ni même d'avoir une nouvelle image de marque mais plutôt de moderniser la gestion et d'assurer une nouvelle dynamique dans l'activité et c'est ce que justement l'équipe de Djibouti Airlines nous promet. "Outre les vols réguliers, nous comptons contribuer au développement du tourisme djiboutien et d'assurer la desserte vers des destinations touristiques grâce à une flotte composée essentiellement d'avions répondant aux besoins du marché local et aux vols régionaux" déclare le directeur commercial, Salam Djebari. Et ce n'est pas tout.

Parmi les actions que la compagnie compte entreprendre pour améliorer la qualité de ses services, la mise en place d'un système de vente et de réservation à distance via Internet. »

[Chris Scott]

I got some of that. Certainly looks like a 500 srs in the photo. With the temperatures in the region, I wonder if they will be using the dreaded de-min water injection system (if fitted). It used to be a pain in the neck when operating charters between the UK and Spain in the summer, but I think we were carrying about 110+ pax.

[pigboat]

I've would have loved to have seen that aircraft re-engined with Tays.

[ICT_SLB]

Pigboat,
One of our FTEs worked on the Dee Howard conversion. He had a video taken inside the cabin in flight - the interior noise was MUCH lower even with the toilets removed. When I was at BAC, there was a proposal to put JT8Ds on in production instead of the Speys - what might have been. Still wonder what an updated 1-11 with RR710s would do.

[Chris Scott]

Yes, the airframe is very robust, I think (like its much bigger stable-mate). The engine, excellent for 1965, was the main drawback by the late '70s. Apart from the noise, the hot-weather performance was embarrassing. You had to load about 80 kgs of de-min water to gain about 200 kgs improvement in RTOW, if memory serves. Net gain, about 1 or 2 passengers.

Guess the Schiphol guys finally knocked the Tay idea on the head with the F100?

[pigboat]

Yes, the airframe is very robust...
Brick outhouse comes to mind. ;)

I remember that Dee Howard proposal. At the time, rumour had it he had been talked out of further development by Gulfstream. A Tay-engined 1-11 would have made the G3 look very unattractive for corporate operators.

A small anecdote about the Spey. My late friend Eric Appleton of RR loved the engine, but he allowed it was Rolls-Royce's greatest momument for turning expensive petroleum products into noise. :)

[Roy Bouchier]

"A small anecdote about the Spey. My late friend Eric Appleton of RR loved the engine, but he allowed it was Rolls-Royce's greatest momument for turning expensive petroleum products into noise." :)

I think the Dart did it better!

The expert in the States on 1-11s was Arthur Trowbridge if he's still around. He was originally with Hunting and knew everything about them, working as a free lance consultant for the corporate operators. Based in Texas if I remember correctly. He would most certainly have the answers.

[pigboat]

I think the Dart did it better!
Fair point, but the Spey did it faster. :D:D

Eric was with RR in Montréal, then was seconded to Mohawk when they acquired their BAC1-11's. It was supposed to be a six-month leave, but he was still there 20 years later. He also instructed on the Dart at the then Allegheny Airlines, after the merger of the two, which is where I met him.

[Chugalug2]

Chris Scott:
Guess the Schiphol guys finally knocked the Tay idea on the head with the F100?

Chris, I seem to remember when hopes were pinned on a commercial as well as a business re-engine programme that word was it was BAC (as was) that put the mockers on it. Seems they thought it would inhibit sales of the new 146. As has been said the originally envisaged 1-11, 2-11, 3-11 series could have done what the MD series later did. The real fly in the ointment was Concord(e) of course. Built in Mr Wedgwood Benn's fiefdom and requiring all the R&D dosh available as he was MinTech or suchlike. So the production line was packed off to Bucharest, where 10 were constructed in 9 years, or was it 9 in 10?

[Chris Scott]

Hi Chugalug2,

You may well be right, at one point, and I did say "finally". I see the Djibouti photo shows evidence of the hideous hush-kit. [Could anyone ever detect any reduction in the noise as perceived by the human ear?]

Remembering the chronology is so often the problem, isn't it? The 146 was originally DH146, then HS146 (Hawker Siddley, for the uninitiated); so not sure BAC would have wanted to defer to it at that stage. Later on, it certainly rings a bell.

Not sure the MD80 series is a valid analogy for the BAC 2-11 and 3-11 proposals, though. The Spey got up to about 12,000lbs thrust. Wasn't the 2-11 going to use 2 tail-mounted engines of about 40,000-lb thrust; possibly RB211s? Even if not, I'm fairly confident that the 3-11 was of comparable size and configuration to the later A300, which started off with CF6s of about 50,000lbs. By that time, the RB211 had run into its carbon-blade debacle, which had delayed and crippled the L-1011 Tristar; and bankrupted RR.

[Apologies to Qu'est-ce-qu'il-dit and the moderators for the (further) thread drift.]

[dixi188]

BAC 1-11 electrical system was designed be a chap called David Jones (so he told me) at Weybridge. I think it was the first airliner with "Split Bus" 3 phase system which most types have followed since. Previous types had parallel systems where all generators fed the same main busbar.

When I was an apprentice at Hurn (69-73) various developments of the 1-11 were proposed including the -700 with "Re-Fanned" Spey (later Tay)
with seats upto about 140, the -800 with GE engine with seats upto 160, and the X-11 which would have had a six abreast cabin and seats for about 180.

The BAC 3-11 would have been about the size of the Airbus A310 with mixed class seating for about 180, and all tourist for about 250.
It was to have had RR RB211-22's initially, the same as the Tristar, to cut development costs. Stretched versions were on the drawing board.

As stated above the Concord was sucking all development money and even though the 3-11 had letters of intent from 4 airlines including American and Braniff and would have been in service a year or two before the A300, it was scrapped.
Another missed British oppertunity.

As an aside, the only good thing about this is that the 3-11 was to be 2 crew from the start and if it had been built there might be a lot of them as freighters now instead of A300's and I might not have a job as Flight Engineer.

Happy days.

[411A]

I think it was the first airliner with "Split Bus" 3 phase system which most types have followed since. Previous types had parallel systems where all generators fed the same main busbar.


Ahhh, well no, it certainly was not.The B707, the first American jet airliner to enter commercial service had a split buss electrical system.
Several each, DC & AC.
Quite reliable, too.

[Chris Scott]

Happy days indeed, but for all the bright ideas that never came to fruition.

You two have got me thinking. What I remember about the Seven-oh was that the F/E used to have to do something clever with the AC generators before each one could be introduced on to the buses. I think they had to be synchronised. This was, thank goodness, quite unnecessary (or done automatically?) on the engineer-less One-Eleven. As far as I can remember, the F/E had no such task on the VC10 either.

Going to have to ransack the garage again. Watch this space...

[TheChitterneFlyer]

How much info do you need?

Here's a small taster...

AC Generation and Distribution
The three generators are driven at a governed speed which ensures a nominal 400 Hz output. During normal operation, the main generators supply power to their respective AC main busbars (Nos.1 and 2) through associated circuit­ breakers (GCBs).

Each main AC busbar supplies its own distribution system. If one generator becomes inoperative or disconnected from its busbar, both busbars are automatically connected together by a split system breaker (SSB), and one generator supplies both No.1 and No.2 busbars. If the APU is running, the SSB remains open and the APU generator automatically substitutes for the off­line generator through an associated GCB (No.1A or No.2A). If the APU is started after a main generator failure, the SSB is automatically opened before the APU generator comes on-line. Fault protection facilities protect each channel from the following faults: ­


Over-voltage
Voltage instability (stability protection)
Differential current faults (differential protection)
Under/Over-frequency
Under-voltage
Over-current
The fault protection circuits automatically disconnect the respective generator from its busbar by opening the associated GCB when any, or a combination of any, of faults 1 to 5 are sensed. If an overcurrent fault is sensed by No.1 or No.2 generator, the alternative generator is prevented from taking over the defective busbar by automatic locking-out of the SSB. In addition, the accompanying under-voltage and/or under-frequency fault opens the associated GCB. In the case of the APU generator, No.1A or No.2A GCB will close, and on sensing the fault both GCBs will trip automatically.

For under-frequency/over-frequency and under-voltage faults, without over­current, a generator will automatically come on-line when the fault clears.

The under-frequency and under-voltage conditions automatically effect generator disconnection from its busbar during engine shutdown.

To reinstate a generator after over-voltage, stability protection, differential protection or over-current faults, it is necessary to select RESET on an associated generator control (GEN) switch. A selection of TRIP, on the generator control switch, disconnects the associated generator from its busbar. A reset selection is then necessary to reinstate the generator.

Amber generator failure (GEN FAIL) warning lights (one for each generator) give a visible indication when the associated generator is disconnected from its busbar, but the supply circuit of the APU GEN FAIL warning light is so arranged that an APU generator failure will not be indicated when both main generators are on-line.

A red BUS FAIL warning light is provided for each AC main busbar to provide a visible warning if the associated busbar voltage falls below a pre-determined value. The lights are connected to the master warning system.

KVA meters (one for each generator) indicate the total power supplied by the associated generator, and a frequency/voltage selector switch with five positions (EXT, GEN 1, APU GEN, GEN 2 and ESS) is provided to monitor the selected supply.

I have more if you need it.

TCF

[Wodrick]

TCF - nice concise description, I did 1-11 electrics in 1973 with a guy called Colin Webster in CWL, by the end of the course we had to draw the bus bar layout or fail ! I've been sat here for a couple of days trying to remember what the SSB was called ! thank you.

Chris - On the 707 and 727 the generators were connected in parallel onto the "Tie Bus" the F/E had to manually parallel the generators before connecting them to the tie bus, remember the pulsing neon lights ? The AC bus bars were then fed from sections of the tie bus and could be isolated by judicious use of the "bus tie breakers" under fault conditions normally perated in parallel however.
Never really had much to do with 747 classics but seem to recall they were similar except that the paralleling was automatic.

[NG_Kaptain]

Wodrick beat me to it.. Was on the 70 in my early years and remember some of the lazy flight engineers used to disregard the flashing lights and just hold the GB switch up til they closed, not guilty of this habit though. Such memories (sorry for thread shift):)

[Chris Scott]

Thanks, TheChitterneFlyer and Wodrick,

That visit to the garage seems less urgent now. Your info backs up dixi188's point about the 2 AC Main Buses on the One-Eleven being separate and autonomous, except in the single genny case; very different from the 707. From what I remember, it was a very nice system that even we pilots could get our heads round - and rather like the A320.

If memory serves, you can also isolate the AC generator field windings with a GCR switch (?) and, of course, disconnect the generator's CSD (constant-speed drive). The latter is actually a CSD-S, doubling as an engine starter (using air from the APU or an external air truck, just like aircraft today) The CSD-S is connected to the N2 (HP) accessory gearbox of the Spey engine by a somewhat fragile shaft. During engine start, this is what produces the classic shriek, its pitch rising with N2 rpm, until the starter dog(?) disengages at a certain rpm. At this point, there is often a momentary hesitation in the scream before it mercifully dies away. [Particularly welcome if you are having to stand under the engine to hold the start (air) valve open manually, in the event of a faulty solenoid.]

For the uninitiated, it is the CSD that controls the generator speed (regardless of engine N2 rpm); hopefully giving a steady 400Hz for the AC electrical system. This is the note (pitch) of the hum you are constantly aware of in an airliner cockpit. One of these days I’ll find out what note it equates to on a musical scale, but it is slightly below (flatter than) the “A” that an orchestra tunes to. If the note falls in pitch (i.e., below 400Hz), one of your gennies may be about to drop off line.

As for the B707, maybe 411A didn't recall the fact that − unlike the One-Eleven − the BTBs are closed in normal operation, effectively de-segregating the different parts of the AC system into a big daisy chain. After my post late last night, disjointed bits of it - including those flashing lights - were floating through my mind as I dozed off. The "enj" certainly works for his keep. The Seven-oh has so many other evolved idiosyncrasies for the successors of Wodrick and NG Kaptain to play with, including splitting the inner and outer flaps electrically to cope with a jammed-stabiliser landing. Phew! Don't the VC10 F/Es have it easy by comparison? [Can't comment on the A300.]

[TheChitterneFlyer]

As for the AC Emergency and DC side of things...

AC Emergency Generation and Distribution
A static inverter is supplied from the DC essential busbar via a static inverter control relay, and connected on its AC output side to the AC essential busbar via an AC change-over relay.

A STATIC INVERTER TEST switch and a magnetic indicator (MAIN, amber, INVERT) are provided which, in conjunction with the AC change-over relay, enable the static inverter to be tested.

During normal operation the static inverter is isolated from both busbars; the AC essential busbar is supplied from No.1 AC main busbar, and the magnetic indicator displays MAIN. If power fails on the No.1 AC main bus­bar, or the test switch is held in the TEST position, the static inverter is automatically brought into operation to maintain the AC essential busbar and the magnetic indicator displays INVERT.

DC Generation and Distribution
The main DC power supplies are normally provided by No.1 and 2 TRUs which are supplied from the No.1 and No.2 AC main busbars respectively. The output of No.1 TRU connects directly to the 28V DC essential busbar and the output of No.2 TRU connects directly to the 28V DC main busbar.

Power for starting the APU and, if both TRUs fail, maintaining the essential services, is provided by two 24V batteries which are connected in parallel to a battery busbar.

When the DC essential and the DC main busbars are 'live' they are automatically interconnected by a main busbar isolation relay. The DC essential and the battery busbars are normally interconnected, via a battery isolation relay, through operation of a control switch (BATTERY) on the roof panel. The battery isolation relay can also be closed by selecting either the fuel load control switch to ON or the DC hydraulic pump switch to BRAKE ACC. A BATTERY MI is provided to indicate (OFF) when the battery busbar is disconnected from the DC essential busbar.

During normal operation all three DC busbars are interconnected, but if the busbar voltages fall below approximately 24 volts, the main busbar isolation relay is automatically opened to isolate the DC main busbar. Thus, if both TRUs fail, the DC essential and the battery busbars are maintained by the batteries. A red DC FAIL warning light gives a visible indication when the DC main busbar isolation relay is open, thus indicating a DC failure. This light is connected to the master warning system.

A DC voltmeter (DC VOLTS) is normally connected to the DC main busbar and therefore normally shows the voltage on this and the DC main busbar. The PUSH FOR BATT VOLTS button transfers the voltmeter to the battery busbar thus showing the voltage on this provided the battery switch is OFF. Otherwise the voltage will be the same as if the button were not pressed. Each TRU has an associated ammeter (TRU AMPS) which indicates the current the respective TRU is supplying to the system. A single charge/discharge ammeter (BATT AMPS) serves both batteries.

TCF

[NG_Kaptain]

Or splitting the inner and outer spoilers to obtain the same results. Was a gem though. Did think the 1-11 was a cool aircraft, our competition had them, we had DC9's.

[TheChitterneFlyer]

Did someone mention flaps?

DESCRIPTION

The flaps are divided into three sections at the trailing edge of each wing and are operated by a hydraulically driven control unit in the fuselage, through bevel gearboxes and shafts to screw-jacks between and at each end of each flap section. Two transmission systems are provided to drive the flaps, a primary and a secondary system. In the event of a primary shaft failure, which is indicated by an amber warning lamp located in the centre instrument panel, the secondary system takes up the drive. Reserve hydraulic power is available from the AC pumps and in an emergency the DC pump will provide sufficient hydraulic power to obtain a 20° flap setting but will not then retract the flaps.

The control unit contains two hydraulic motors independently powered by No.1 and No.2 hydraulic systems. The motors are geared in parallel to a common output shaft which is connected to the primary and secondary transmission systems in both wings. The left side of the output shaft is connected to the left wing primary and right wing secondary transmission. The right side of the output shaft is connected to the right wing primary and left wing secondary transmissions.

The secondary transmission system is not normally carrying any load. Backlash is provided to permit the system to lag slightly behind the primary system but taking up the load outboard of a primary system failure. If one hydraulic system fails, the flaps can still be operated with a reduction of operating speed. If both hydraulic systems fail, a hydraulically operated mechanical brake within the flap control unit holds the flaps in the selected position.

A flap lever on the centre console controls the two hydraulic motors in the flap control unit. The lever is gated in the following positions UP, 6°, 13°, 20°, 26°, and 45°. A baulk at 20° requires a release of the lever and subsequent reselection when moving through this position. This prevents the inadvertent selection of more than 20 flap for take-off; it also aids the rapid selection 20 flap when overshooting. A flap position indicator which shows the position of the flaps is located on the centre instrument panel and is operated from a transmitter mounted on the starboard outboard No.4 screw-jack.

OPERATION

When the flap lever is moved to a selected position, the movement is transmitted by the cable circuit to rotate a pulley in the flap signalling mechanism. The pulley moves a cam which operates a lever connected to the flap control unit input shaft. Mechanism within the control unit operates valves controlling the operation of the hydraulic motors.

The primary drive shafting is connected to the input shaft of each screw-jack head through right-angle bevel gearing to drive the screw. As the screw rotates, the nut body moves along the screw and moves the attached flap carriages.

A hydraulic lock on each motor maintains the flaps at the selected position until a further flap selection is made.


TCF

[TheChitterneFlyer]

Or Spoilers/Speedbrakes?

DESCRIPTION

The term 'speedbrake' is used in a general sense to identify the spoiler/speedbrakes for the sake of brevity and to agree with the control markings. Where precise definition is necessary, 'spoiler' or 'speedbrake' is used.

The spoiler/speedbrakes are fitted in four independent sections, an inner and outer section on each wing. Each section is hydraulically operated by its own power control unit and linked by a pilot operated mechanical control system. No.1 hydraulic system powers the outer sections and No.2 system the inner sections, thus failure of one hydraulic system does not cause complete loss of speedbrakes.

Controls in Fuselage
On the centre console, the single control lever is fitted with a movable collar; a damper is attached to the control lever and the lever is linked by a push-rod to a cable quadrant. From the quadrant a cable circuit extends rearwards to a drum on the rear face of the fuselage torque box.

Controls in Wings
From the drum a cable goes to the upper of two pulleys on the mixing unit in each wing. From the lower pulley a second cable is led outboard around an idler pulley and back to the drum. On the port side only, the cables are crossed between the torque box pulleys and drum. A swinging arm, on which the mixing unit pulleys are mounted, is linked by rods and levers to a torque shaft assembly, comprising inner, centre and outer portions. The inner power control unit is connected to the outer portion of the torque shaft by links, bell-crank levers and the inner spring strut; the inner power control unit ram is attached to the inner section of the speedbrakes.

The outer power control unit is connected to the outboard end of the outer portion of the torque shaft by links, bell-crank levers and the outer spring strut; the outer power control unit ram is attached to the outer section of the speedbrakes. A follow-up mechanism cancels the input signal after the ram has moved to the selected position.

OPERATION

Speedbrake Control
The movable collar on the control lever is raised for take-off and landing, to allow full speedbrake (50°) to be selected for landing or for an abandoned take-off. The collar is pushed down in flight to prevent a speedbrake selection of more than 20°. This limited angle is not operationally embarrassing and improves lateral control in the event of inadvertent flight above VMO. Movement of the lever on the centre console is transmitted to the mixing unit pulleys in each wing. Pulley movement is changed to rotary movement in the torque shafts, and through spring struts operates the servo valves of the control units. Control system movement opens a rotary valve thus directing supply pressure fluid to one side or the other of a jack ram piston, which moves the ram body and consequently the control surface. Movement of the ram body is proportional to and in the same direction as the movement of the pilots' control input. When the control input ceases, a feed-back movement restores the rotary valve to a neutral (shut-off) position, thus preventing further control surface travel.

The control units regulate the flow of fluid to actuate the rams. If the aircraft exceeds the speed for speedbrakes extension they will blow back, but will gradually extend as speed is reduced. If a servo valve fails, the relevant spring strut will 'collapse' and operate the micro-switch, which will put on the associated fail warning light on the centre instrument panel. The warning lights are cancelled by moving the adjacent spoiler isolate switch to off. This will allow the affected spoilers to blow back.

Aileron/Spoiler Control Mixing
When used as spoilers, the appropriate surfaces move upward in conjunction with the upward moving aileron but remain stationary on the other wing. Mixing the aileron and spoiler control is achieved by input of the aileron control circuit being fed into the spoiler quadrants and of the mixing pulleys. Upward movement of the ailerons, above approximately 4° of aileron movement (11-15° of control wheel aileron movement), also moves the input lever of the control servo units which, due to the initial setting, delay the operation of the spoilers. With the spoilers extended as speedbrakes, application of aileron will retract the spoilers on the upward moving wing, and further extend them on the downward moving wing.

TCF

[411A]

Nothing especially new, for the time.

B707.
Alternate flap drive?
Yes.
Spoilers used for roll control?
Yes.
Split the spoilers?
Yes.

The 'ole BAC 1-11 was however rather popular as an exec jet in the USA.
Nice roomy cabin.

[forget]

Nothing especially new, for the time.

How about two crew? :hmm:

[Krakatoa]

It is just like being back in the class room on the 111 course.
I even dozed off at my computer !

[411A]

How about two crew?

For a small(er) twin jet, two crew was standard, for the time, Caravelle excepted.

Large heavy jet (which the B707 definitely was)...4 engines, three crew were the norm.

[Chris Scott]

Krakatoa,

Can only assume you may have been late coming to the One-Eleven. In my day (as late as 1977) it was still "talk and chalk"; and my hand-written notes are still in the garage somewhere. How much is it worth if I promise not to resurrect them?

At least two of the ground instructors at British Caledonian (Gatwick) had been involved in One-Eleven design at BAC: Doug Realff (Hydraulics, L/G and F/CTLs) and Pete Horscroft (Pneumatics & Air Con, but he also taught Electrics). And bl***y good they were too. They were criticised by some (pilots, mainly) for including too much "nice-to-know" stuff, but we missed them enormously in 1984, when embarking on the A310 VACBI at Toulouse. Now that system - with monochrome graphics the speed of slow-drying paint - really could have you nodding off, especially in the darkened rooms. [The only answer was to stroll off to the coffee bar for yet another grande-crême, served by a lady in tight leather trousers.]

TheChitterneFlyer's impressive output is, on the contrary, quite riveting (flush ones, of course). Thanks, TCF.


Hi411A,

You are right about 2-crew being normal on short-haul, although the B737 - which post-dated the One-Eleven by some years - was the first 2-crew Boeing jet.

Yes, splitting spoilers on the 707 was the initial action to assist pitch control with a jammed stabiliser. If it happened at cruise speed, for example, you needed to extend just the outer spoilers as you slowed down. The 707 was/is a fantastic airplane, but its much-evolved 1950s systems were archaic in comparison with the 1960s VC10. And, before you remind us how uneconomical the "Ten" was, remember that fewer than 50 were ever built, so it never had the chance to evolve. The superb 707-320s most of us flew in the 1970s were the result of resourceful tweaking of tweaking. The overall concept was classic brilliance; the cockpit and systems mainly agricultural. They wouldn't stand a chance of type certification today, because there is so little redundancy in some key areas. Operating them was a challenge; when you got it right it was rewarding.

The One-Eleven, on the other hand, got its systems right from the start (as did the 3-crew VC10). Yes, it had a deep-stall problem that was duly overcome. Yes, it was soon in need of further stretching and a more competitive engine. Yes, the money wasn't available in post-war Britain.

[Krakatoa]

The computer was the one I am sitting at right now. Like many others I have spent hours trying to stay awake during lectures on various aircraft electrical systems. Just reading the threads got me going again.
Forty years ago the daddy of electric systems was the Trident. That would cure anybody's insomnia.
Just think about having to learn about the "all electric" Boeing 787 !!

[dixi188]

Crew members.

When the 1-11 was certified in the USA all aircraft with a max weight over 80,000 pounds had to have 3 crew members. That is why the 400 srs. (USA)was 80,000 pounds and the 300 srs. (UK) was 84,000 pounds or there abouts. Both variants were almost identical.

By the time the Boeing 737 came along the rules had changed.

[WHBM]

For a small(er) twin jet, two crew was standard, for the time, Caravelle excepted.
This is the sort of topic that runs and runs here.

When the One-Eleven was introduced, there were no other commercial jets which were not 3-crew. There wasn't much of a choice of shorter-haul jet types then, but the Caravelle, 727, Trident, old Comets and Soviet Tupolevs were around. US operators did their early jet years wholly with 4-engined 707s, DC8s and Convairs on quite short runs until the 727 came along, still 3-crew. The One-Eleven was the first two-crew jet.

Other 2-crew types like the F28 or the DC9 came some time later. Even the first 737s were 3-crew.

[Compass Call]

TheChitterneFlyer

Excellent tutorial. How about -landing gear, apu, engines:ok:

CC

[keskildi]

well, a big ''merci'', thank you to all of you for all this info

I mail it to the lady right away

sorry for the delay replying your messages, I was gone to Singapore, guest on the A380 SQ !

happy landings everybody !

[411A]

Even the first 737s were 3-crew.

A common misconception.

By original certification, the B737 was a two-crew FD.
Only certain union contracts made it three crew.

[keskildi]

Air France being one of these companies....

the resale value ''second hand'' may be a problem, non

sells like a ''twin '' coffin ?

[TheChitterneFlyer]

Landing Gear huh? OK...

DESCRIPTION

General
The retractable tricycle undercarriage is operated by hydraulic power supplied from system No.1. The main and nose undercarriages retract and extend simultaneously and are enclosed by doors when fully retracted. A cable-operated free-fall mechanism is provided for emergency lowering. A nosewheel steering system is provided which incorporates a standby steering system for use when system No.1 has failed or the undercarriage has been lowered by free-fall operation. The main wheel braking system is arranged for foot and hand operation with hydraulic power supplied from system No.2 and incorporates an anti-skid system for the footbrakes only. Gravel deflectors are provided for the nose and each main undercarriage.

Undercarriage controls and indicators are located on the centre instrument panel, the forward cabin intercom area and the left and right-hand consoles on the flight deck. Visual downlock indicators are provided for each main undercarriage and for the nose undercarriage.

Main Undercarriages
The main undercarriages retract inward and are housed jointly in the wings and an unpressurised bay in the fuselage. Three doors enclose each undercarriage when retracted: an outer door, a fixed door and an inner door. The inner doors are hydraulically operated and are retained in the closed position by an uplock mechanism. A panel in each inner door gives access to the bay for maintenance purposes.

Each main undercarriage comprises a shock-absorber strut attached to a pintle supported in the wing torque box structure. The strut is braced by a forestay and a folding sidestay, and is locked down by links held in geometric lock by hydraulic jacks. No uplocks are fitted, the undercarriage being supported in the fully retracted position by the inner doors. Mechanically operated hydraulic sequence valves control the operation of the doors in association with the retraction and extension of the undercarriage. The brakes are automatically applied when the undercarriage selector lever is moved to the UP position. The brakes are released and the undercarriage hydraulic system depressurized, when retraction is completed.

A weight-switch box, fitted to each forestay, is operated by shock-absorber strut extension and compression. Micro-switches in the switch box actuate relays which affect various electrical circuits. An earth wire is attached to the outer wheel brake units, for static discharging.

Nose Undercarriage
The nose undercarriage retracts forward and is housed in an unpressurised bay in the fuselage and when fully retracted is enclosed by doors. It cannot retract until the nosewheels are central.

It comprises a shock-absorber strut assembled in a housing attached to the bay structure and braced by a pair of drag links. Toggle links, operated by a lock jack, lock the undercarriage in the up and down positions. The retraction jack is fitted between the bay roof and an arm on the shock-absorber strut housing.

Spin brake shoes are fitted in the bay roof to arrest wheel spin when the nose gear is retracted.

The mechanically operated doors, two forward and two rear, enclose the under­carriage in the retracted position. The forward doors also close after extension of the undercarriage. The forward doors can be opened to give access to the bay for maintenance purposes.

Steering
The steering system is supplied with hydraulic power from system No.1. Steering handwheels are provided on the left and right-hand consoles adjacent to each pilot's seat position. The handwheels are connected by cables to a steering control valve which directs fluid to and from steering jacks to turn the nose shock-absorber strut. Rotation of the strut actuates a follow-up system of pulleys and cables to restore the control valve toward the neutral position.

Powered steering is limited to 78° either side of the aircraft centre­line, but free castering is possible to 110° on each side.

A cam operated steering and lock change-over valve ensures that the steering system can only be operated when the nose undercarriage is fully extended.
Rudder 'fine' steering is provided to enable the pilot to control the nosewheel steering, in relation to the rudder position, to a maximum of 7° on each side of centre.

A standby steering system is provided for use when system No.1 has failed or when the undercarriage has been lowered by free-fall operation. Hydraulic power is supplied from an accumulator and operated by a guarded switch on the left-hand console, near the steering handwheel. The switch is not effective until the main undercarriage weight-switch relays have operated.

Free-fall Mechanism
A cable-operated free-fall mechanism releases the nose undercarriage uplock and the main undercarriage door uplocks and allows each undercarriage to fall and lock down under its own weight. The free-fall operating lever is located under an access panel in the right-hand console.

Wheels and Brakes
Two wheels are fitted on the nose undercarriage and two on each main under­carriage. Each wheel comprises two half-hubs fitted with tubeless tyres.

Hydraulically operated brakes fitted to each main wheel are arranged for either foot or hand application, hydraulic power being supplied from system No.2. Foot-brake pedal movement is transmitted via master cylinders, at the pedals, to a brake control valve which controls pressure delivery to the brakes and provides for differential braking. The foot-operated system incorporates anti-skid units which permit maximum normal braking application under all conditions without incurring wheel skid. The handbrake system is operated by handles mounted on either side of the centre console. The left handle can be locked in the 'brakes applied' position for parking. Hand operation applies equal pressure to all four brake units, with no anti-skid system incorporated. The brakes are automatically applied when the undercarriage selector lever is moved to the UP position and released when retraction is completed.

In the event of overheating through excessive brake temperatures, fusible plugs incorporated in the main wheel hubs will melt and release the air from the tyre, thus preventing tyre burst. Brake temperature (dual) indicators are provided in the flight deck.

The accumulators are charged with air to 1,000 psi. The auxiliary DC motor driven pump can be used to hydraulically charge the brake system accumulators on the ground for towing purposes and for 'topping-up' the accumulators in flight before an emergency landing, when the No.2 hydraulic system is inoperative. A pressure transmitter connected into the air line to each brake accumulator gives indication of available brake pressure.

Control and Indication
The landing gear UP/DOWN selector lever is located on the right-hand side of the centre instrument panel together with position indicating lights and a warning horn cut-off and test switch which is spring-loaded to the centre position. A spring-loaded knob at the end of the selector lever must be pulled to disengage a latch mechanism before selection. A safety lever, operated by a lock solenoid, prevents normal movement of the selector lever to UP until the aircraft is airborne. The safety lever can be overridden by depressing an override lever fitted under the selector lever.

In the event of failure of the normal indication system, visual indicators show when each undercarriage is locked down. Each main undercarriage indicator is located on the upper surface of the wing trailing edge, and the nose undercarriage indicator is located under a cover in the floor at the rear of the flight deck.

An Undercarriage Doors Warnings & Lights Test Unit (U/C Test Unit) provides further in-flight diagnostic information in the event of a gear or gear door warning. The U/C Test Unit is located on the aft face of the captain’s bulkhead and comprises of a Test Switch (labelled ON - OFF) and six red indicator lights labelled NOSE UP / NOSE DOWN / PORT DOWN / STBD DOWN / PORT DOOR / STBD DOOR. If a ‘gear unsafe’ indication occurs in the cockpit, selection of the Test Switch to ON will illuminate the appropriate warning light associated with the microswitch responsible for the unsafe indication. If none of the lamps illuminate, it is assumed that it is a failure of the microswitch for the gear selector lever.

Gauges are provided to give indication of brake pressures applied, brake accumulator pressures and brake temperatures.
A warning horn will sound continuously during approach and landing when the undercarriage is not locked down and one or both of the following conditions exist: ­


Flaps are selected to or beyond 26° irrespective of throttle position.
Either or both throttles are below the approach rpm position and the speed is below 165 knots.
The warning horn can be cancelled by the HORN CUT-OFF/TEST switch. On mod PM 5366 the GEAR UNSAFE light also illuminates when the gear horn is muted by the HORN CUTOFF switch: the gear horn will sound and the light remain on when flaps are selected to or beyond 26°; the light will go out when the landing gear is locked down or throttles advanced above the approach setting.

SYSTEM OPERATION

Undercarriage Retraction
With system No.1 pressurized and the selector lever moved to UP, the brakes are automatically applied, hydraulic pressure releases the door uplocks and the door jacks extend to open the inner doors. When both doors are fully open, a sequence valve directs the hydraulic pressure to the downlock jacks, the downlocks disengage and the downlock jacks fold the toggle links to 'break' the geometric lock and at the same time folds the sidestay upwards. The retraction jacks then rotate the pintles to retract the undercarriages. When both main undercarriages are fully retracted, the door jacks close the inner doors which engage the uplocks and support the main undercarriages.

The nosewheels are centralised, when the aircraft is airborne, by integral cams in the shock-absorber strut. When central, pressure is sequenced to operate the up/down lock jack which 'breaks' the geometric lock formed by the drag and toggle links. At the same time the common pivot point of the drag links is moved upward, the drag links fold and retraction is initiated. The hydraulic pressure is directed to the retraction jack by a steering centring valve when the wheels have centralised, the retraction jack extends and the nose undercarriage is retracted. The undercarriage is held in the retracted position by a geometric lock imposed on the toggle links.

The undercarriage red warning light on the centre instrument panel illuminates when the undercarriage selector lever is moved to UP. As the main and nose under­carriage downlocks 'break' and retraction is initiated, the three green lights extinguish. When all undercarriages are fully retracted and each main undercarriage inner door uplock is engaged, the red undercarriage light extinguishes, the brakes are released and the undercarriage hydraulic system is depressurized.

A cam-operated micro-switch, fitted near the end of the undercarriage selector lever, is operated when the lever knob is pulled to disengage the lever latch from the DOWN or UP gate. The micro-switch is electrically connected to the undercarriage red warning light, so that when the latch is not fully engaged in the latch gate the red warning light illuminates.

Undercarriage Extension
With system No.1 pressurized and the selector lever in the DOWN position, hydraulic pressure releases the inner door uplocks and the door jacks extend to open the inner doors. When both doors are fully open, the hydraulic pressure is sequenced to the down side of the retraction jacks which in turn rotate the pintles and extend the undercarriages. Spring-loading on the down lock jack re-imposes the geometric lock on the toggle link. When each undercarriage is locked down, hydraulic pressure is again sequenced to close the inner doors and engage the door uplocks.

Simultaneously, hydraulic pressure is directed from the 'lower' line to the down side of the nose undercarriage retraction jack via the steering lock and change-over valve to 'break' the uplock. The jack extends the nose undercarriage and when fully extended a geometric lock is imposed on the toggle link.

The U/C unlocked RED warning light illuminates when the undercarriage selector lever is moved to DOWN. When all undercarriages are fully extended and the downlock on each undercarriage engaged, the GREEN light in each of the three indicators on the centre instrument panel illuminate. The main undercarriage inner doors then close and when both the door uplocks are engaged the RED U/C unlocked light extinguishes.



Steering
When the nose undercarriage is fully locked down, the steering and lock change­ over valve is mechanically actuated to allow pressure from the 'lower' line to pass to the steering control valve.

Manual movement of either handwheel is transmitted via cables and a feedback assembly to move the steering control valve from its neutral position, thus connecting one side of each steering jack to return. Pressure present on the other side of each jack causes the jacks to rotate the shock absorber strut in the strut-housing. The subsequent movement of the nosewheels drives the follow-up cables, linkage and the feedback mechanism, to restore the steering control valve towards its neutral position.

With the steering handwheel held stationary, the displacement of the control valve from neutral is maintained. When the handwheel is released, the control valve returns to neutral under influence of a centring spring leaving the nosewheels free to castor.

Rudder 'fine' steering is limited to 7° on each side of the aircraft centre line and is only operative with the undercarriage in the down position and the nose shock-absorber strut compressed. With the undercarriage lowered, a clutch is operated hydraulically, connecting the rudder pedal linkage to the steering cables. Thus steering is achieved through a limited range from the rudder bar, using the normal steering system. Movement of the steering handwheel overrides the signals from the rudder bar.

Standby Steering
The standby steering supply should only be used for landing if the landing gear free-fall system is selected or if pressure is not available in the No.1 hydraulic system and provided that a steering handwheel is held in readiness to prevent nosewheel movement during landing.

The standby steering supply should be selected after the nose landing gear has been locked down, and prior to landing. Following a selection of the standby steering supply, power is not available at the steering cylinders until the main gear oleos are compressed. .

The standby steering accumulator is normally hydraulically charged by system No.1. With the standby steering switch in the ON position and the main undercarriage weight-switch relays actuated, a selector valve is energized to connect the accumulator through the control valve to the steering jacks and steering is effected by normal operation. On completion of landing the standby steering must be switched off. It is important to ensure that it is switched off during all normal operations.

If the accumulator pressure falls below 2,000 psi, irrespective of the standby steering being switched on or off, the warning light illuminates.

Free-fall
When the free-fall lever is pulled upward, the nose undercarriage uplock and the main undercarriage door locks are mechanically released, allowing the undercarriages to lower under their own weight.

The undercarriage control valve is mechanically operated, irrespective of the selector lever position, and the pressure supply is blanked off. The 'raise' and 'lower' lines are connected to the return line and fluid is released from the main retraction jacks, allowing the undercarriages to lower freely. The main wheels push the inner doors open and the doors remain partially open after the undercarriages lock down, leaving sufficient ground clearance.

The position of the undercarriage selector lever does not affect free-fall operation, but it should be left in the DOWN selection and must be in this position before the free-fall lever is reset.

Wheel Brakes
When the footbrake pedals are depressed at either pilot's position, master cylinders transmit the movement by servo pressure to actuate a brake pressure control valve which regulates pressure delivery to the brake units and provides for differential braking.

With No.2 hydraulic system inoperative, the footbrake accumulator provides one full braking stop with the anti-skid units operating.

The anti-skid system is an integrated mechanical-electrical-hydraulic system which controls the aircraft hydraulic brakes to obtain the maximum aircraft retardation under all runway conditions.

Mounted within each wheel axle, and driven by the wheel, is a wheel speed transducer which provides a signal proportional to wheel speed; this signal is fed to the control shield. A dual pressure control valve feeds braking pressure to each main wheel, in conjunction with the control shield, to control excessive brake pressure and to provide wheel protection with optimum braking control.

With the anti-skid system switched on before touchdown, brake application cannot be achieved until the wheels have commenced rotating and the weight switchbox relays have been operated, even if the touchdown is made with the footbrake pedals depressed.

Thermo-couples connected into the brake units give indication of brake temperatures through the brake temperature gauges.

When a handbrake handle is pulled, a cable-operated control valve is actuated and permits an equal pressure to be applied to the four brake units. For parking, the left handbrake is pulled and turned to apply the brakes. On undercarriage retraction, an auto-brake jack is pressurized and actuates the control valve permitting a pressure delivery to the brakes. The handbrake accumulator provides a minimum of six full brake applications with No.2 hydraulic system inoperative.

Weight-switch Operated Circuits
Compression of the shock-absorber struts on landing, and extension on take-off, operates the weight-switch box and the following circuits are affected: ­


Undercarriage indication and lock control.
Stall warning system.
Waste water anti-icing.
Air conditioning ground cooling.
Ice detectors.
Airfoil anti-icing.
Configuration warning.
Generator cooling.
Standby steering and LP warning.
Elevator isolate.
Anti-skid system.
AC hydraulic pumps.
Flight voice recorder.
Galley supplies.
Lift dumper.
Flight data recorder.
Engine start and CSDS control.
Ground proximity warning.

[Krakatoa]

And the point of reproducing this would be...?

[forget]

411A By original certification, the B737 was a two-crew FD.
Only certain union contracts made it three crew.

Am I missing something? 3 crew 737. :confused:

[TheChitterneFlyer]

Krakatoa... my apologies for boring the pants off you; someone asked for the info; I volunteered it!

Should anyone require any further info please do PM me; I'd so much hate to divert from the original thread. Typical PPrune... someone not understanding what was originally asked for.

TCF

[Fly380]

I understand that the most complicated electrical system ever was the Bristol Britannia. I flew that back in the very early 70's and the 1-11 in the 80's. The ARB technical exam was a nightmare on the Brit. The 1-11 was simple in comparison. It was the wiffle tree that got me on the 1-11.:ugh:

[Chugalug2]

Forget: "Am I missing something? 3 crew 737. :confused:"
Not really, Forget, more to the point the unions that forced it upon their hapless managements did, I would say. It was merely the airborne equivalent of the fireman, or "second man", rostered by BR on diesels where there was no fire to tend, but none the less he had a seat, a windscreen wiper, and an oven to heat the pies in!

[WHBM]

It was merely the airborne equivalent of the fireman, or "second man", rostered by BR on diesels where there was no fire to tend, but none the less he had a seat, a windscreen wiper, and an oven to heat the pies in!
Surely the Lufthansa 737-100s, the first built, had a Flight Engineers console. There are several references to this but I can't find a photo.

Some early US 737-200 users (United, Western, Piedmont) did initially have the "seat with nothing to do" arrangement which was a union thing.

[forget]

Surely the Lufthansa 737-100s, the first built, had a Flight Engineers console. There are several references to this but I can't find a photo.

Just 30 series 100's were built, with 22 going to Lufthansa, 5 for Malaysia (Singapore) Airlines and 2 for Avianca.

Interesting. I often flew on the flight deck of MSA's 737s. I thought they were 200s - but they had only two crew. I'm sure there was never a Flight Engineer's console on any 737.

PS. ChitterneFlyer, disregard Krakaprat.

[keskildi]

a big thank you to all of you PPRunners for the information I gathered on the subject on behalf of that lady friend

the handbook came in the mail this morning...

happy landings everybody !