Link Train daft idea...

[John Hill]

In our aviation museum we have something more than one and somewhat less than two Link Trainers.

One is assembled complete and set up for display but is deemed too 'fragile' and/or valuable to demonstrate in operation. The rest is a pile of various bits but not enough to make an operating trainer.

Now the daft idea is maybe we can use the pile of bits to build an operating "Link Trainer" by incorporating more modern and easier to acquire computer, pneumatic and hydraulic bits.

Does anyone know of anyone having built such a hybrid?

Thanks

[XH175]

Hi John,


A few D4 fuselage have been converted to simulators with no actual degrees of movement.


The height of the panel usually precludes projection of scenery on a background which detracts from the flight experience.


Computer driven off the shelf sim instruments are more usually used than converting the telemotor originals.


As long as you have the slipring column then simple movement can easily be replicated using modern vac valves instead of the original valve block. Bellows can be fabricated from scratch using modern materials.


Conversion is possible for the D4 but normally it is just the wooden structure, panel, flying controls and seat that are used for a non moving device. I did see one conversion that used the fuselage and 4 hydraulic rams supporting the fuselage from the floor. This induced pitch and roll movement with washout to give an impression of continued movement but it needed visual aid to continue the illusion.

Earlier type Links (AN-T-18) with the hinged lift up hood are better suited to conversion being simpler internal gubbins and the ability to give a projected background which is easily visible from the seat for pilots of all ages.


If at the end of the day your museum is looking to dispose of parts from a D4 then I'm looking for radio aids gear, fuselage amplifier, turn and bank takeoff bracket, engine simulation valves and two fuel contents gauges for a D4 that I am restoring in the UK.


Regards
Ross

[John Hill]

Hi Ross

Thanks for the information and responding so quickly, I dont even know what version we have but it would have been installed here when Ashburton, (New Zealand) was an EATS primary training location in WWII.

I was actually hoping that someone might have converted one to do the original job which was to simulate instrument flying and maybe even drive the spare desk top crab we have on hand. There would of course be no projected scenery etc. Presumably there is information available to show what electrical signals are required to drive the various instruments including the crab. You mentioned 'sim instruments', are these period style instruments modified for easy computer interfacing, I will Google them right now.

Of course I am perfectly prepared to accept that this is really an unrealistic project for us but I thought I should at least ask if others have done it.

Unfortunately I dont think we have any of those parts surplus but I will be out there tomorrow and I will take a look. I must say though that being a community supported all volunteer museum trading or selling stuff we have been given is always a real minefield.

John

[dubbleyew eight]

back in the early 70's one of the hangars in Albury had an almost functional link trainer in it. we pre solo sprogs would get the key and sneak off for a play in the link trainer.
I have memories of an almost intoxicating spruce varnish darkness as we played with instrument flight in it in the heights of an australian summer.

come to think of it a link trainer and a dehavilland rapide have almost the same intoxicating cabin aroma. :ok:

restoring a link trainer to usable is not a daft idea.
they are a wonderful piece of aviation history.

btw no scenery in a blind flying trainer mate.
the table is a plotting table that the trainer plots the flown course on.
this is Duxford's Link Trainer
http://i1274.photobucket.com/albums/y421/dubbleyew8/DSC00725_zps66b6ffae.jpg

[John Hill]

Ours looks like that Duxford one but they do not have the map and crab on the table?

[XH175]

Hi John


The hydraulic movement platform was a home brew similar to the last picky on this page.


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Electric Sat dish actuators can be substituted but weight needs to be supported with a central universal joint.



Sim kits are the most popular for instruments


SIMKITS - Flight Simulator Hardware (http://www.simkits.com/)


You can always substitute photographed period instrument dials for the sim kits modern equivalents reusing the drive gubbins.


Easiest way to tell a D4 type is by the canopy. If it slides back and forwards you have a D4 or US equivalent from the 1950s. They come in piston and jet flavours.


If the canopy lifts up, hinged on the starboard side then it is an earlier mark from the 1940s. Piston flavour only.


The Link was designed as a radio aids trainer with instrument flight simulation as a secondary function. If you take away the radio aid training feature then the flight simulation that is left is fairly crude by modern computer standards.


The general public will need and expect visual display to accept the experience as a "flight simulator" and the Link was just not set up for this.


I have seen static D4 cockpits that fitted out with a glass cockpit (flat screen) and used as gunnery simulators. Very popular with the kids (small and big).


Oh and the problem with unattended crabs is that they wander off and throw themselves lemming like at the floor given any unwatched moment!.


Everything is possible just needs the first step and trial error experimentation.


D4s are the most common type in the UK in public hands. The early types went to museums but the D4s were released to flying clubs and ATC units before being sold on. Hence the predominance of this type in the stripped down format being used as sim chairs.


This is my D4 fuselage, the desk, base and octagon are elsewhere in the workshop.


Link Trainer D4-030 Restoration Thread (http://forum.keypublishing.com/showthread.php?128275-Link-Trainer-D4-030-Restoration-Thread)


If you PM me an email address I'll dig out the D2 type (Hinged canopy) manual when I'm next in the workshop and email a copy over.


Regards
Ross

[oldpax]

When were they last used?I maintained the link at RAF Oakington up to 1966 and it was still in use in 1968 when I left the RAF.

[John Hill]

Ross, ours is definitely piston only, this was a DH82 training station. The trainer has a side lifting canopy.

I know you are right about the general public and their expectation of visual displays etc and we have that on a Microsoft flight simulator in a little plywood fuselage someone has made but I was wandering around in my mind thinking that the basic instruments and driving a crab on the map would be something quite different.

That is a nice looking hydraulic platform.

The SIMKITS are very smart too and obviously very easy to set up and use but those prices are way out of our reach, it is nice to dream though!

I doubt that these have been used since about 1950.

[XH175]

Homebrew instruments come in well below the Sim Kits off the shelf price.


I recommend the books from this guy as Ikea style designs that are easily fabricated from r/c servos and homebrew/scrap printer stepper motors.


Just click on the book picky for photos of the basic instruments produced to his plans.


Mike's Flight Deck Books (http://www.mikesflightdeck.com/mfdb/mfdb.html)


The D4 MkI piston model was in RAF service until the 1960s when it was phased out for the D4 MkII jet model. The MkII was phased out of service use in the mid 1970s. It was one of the released models that I first cut teeth on.


A special variant of the MkII was produced specifically for Gnat training simulation.


Regards
Ross

[BEagle]

The MkII was phased out of service use in the mid 1970s.

I recall many hours sweating away during my JP course on those hissing monsters!

A trick to play on ones chums was to use the little switches outside to cause pitot head icing, followed by a flame out. Those too dull to notice would soon find themselves stalling; the Link would give a large wheeze and tip forwards, much to the occupant's surprise!

[XH175]

Hi BEagle


Pitot icing was one a number of progressive failures that could be applied by those with evil intent.


Flicking the icing switch on the fuselage instructor panel "froze" the ASI reading and all that the pitot heater switch on the panel did was to illuminate a lamp under the starboard rear side of the trainer fuselage. It needed Instructor action to switch off the icing switch to return the ASI to dynamic reading.


Silent application on and off during a SBA along with selective toppling of horizon could induce over correction from the cocky student victim and uncontrolled ground interface.


Another favourite was that the instructor had control over the radio aids static and could both fade signals and overlay with levels of static that mirrored EMP air burst.


Here is the AP image of a shiney D4 MkI, factory fresh along with the desk/overhead and base/octagon.


http://www.rafaircraftaccidents.com/DSCF0516.JPG


Not a bad design from a chap using player piano motors from his family factory.


The bellows cloth I use in the restoration is from an Organ restorer. When he heard the quantity I needed his quote was "that is one immense organ" seemed quite appropriate for what I heard Links called in service!


Regards
Ross

[Wander00]

Where was the Gnat version - don't recall it at Valley mid 60s, but I DO remember the sim!

[XH175]

Do not know where they were located but the AP for them was produced


AP 1697G Vol 1.


a copy survives in The National Archive


Link instrument flight trainer type D4 with Gnat instrumentation: general and technical... | The National Archives (http://discovery.nationalarchives.gov.uk/SearchUI/Details?uri=C3306651)


AIR 10/5825


Regards
Ross

[Rosevidney1]

A favourite trick on the Mark 1 was to turn on the 'rough air' switch after locking the canopy down on some poor unfortunate trainee.