Special Cabinet Enclosure for Cranfield Aerospace

Cranfield Aerospace is looking to SRS Products for a special cabinet enclosure.

Cranfield Aerospace has an established world-class reputation in the aerospace industry and one of its major activities is the design and manufacturer of motion cueing seats used within flight simulators for pilot training.

The company is currently completing a contract to design a motion cueing system to train Tornado G24 pilots.

The motion cueing seats are to be used in a fixed-based simulator, which is an absolute replica of the cockpit of the aircraft to be flown.

Being fixed based, Cranfield's approach is to take either an actual aircraft or replica ejection seat and engineer it to what is called a motion cueing seat (or G24 seat).

This comprises four axis's of simulated motion which are provided by DC brushless motors buried within the seat frame itself.

The objective is to make the seat appear to all intent and purposes look like a genuine aircraft seat, to the training pilot.

Along with all the DC brushless motors and associated seat equipment is the DSP based controller, interfaces (host, user and safety), and enclosures etc., Up until now virtually all of this equipment has been either engineered on site or where feasible, bought in and modified.

A typical example of the latter has been the cabinet enclosures.

But along with the need to modify these enclosures to combat RFI radiation.

It was therefore decided that this time Cranfield Aerospace would move away from using modified cabinets and go to purpose built enclosures.

Tenders were invited.

SRS Products was the first company to respond and not only that came up with what was considered to be a good solution using the company's new CUBIC enclosures.

The attractive styling of CUBIC was considered an added bonus.

The problem that Cranfield Aerospace had with its enclosures was that this time the company required a 14U size.

The Cranfield engineers surfed the net and all the catalogues they could find for a size 14U.

However, as enclosure manufacturers regard 14U as non-standard, most offered a 15U - which was unacceptable due to an overall height constraint.

In the end there were only four or five manufacturers who were prepared to consider producing a non-standard size and most of those were going to have to refer back to their 'sister' companies in Europe.

Against this, SRS Products had responded within a few days with a price guide and a solution, which impressed Cranfield.

Its designers visited Cranfield within a week of the original request and, says Graham Campion - Cranfield's Business Development Manager for the Simulation Product Development Group.

"We felt that they were people we could work with and we got together and came up with some reasonable ideas to solve the engineering problems encountered".

One of the interesting engineering problems encountered was a special back panel for the connectors to pass through.

On the tall cabinet, the doors are double skinned for EMC purposes, but there has to be a connection between the two skins.

That was very well achieved.

Graham Campion continues "For us the major appeal of CUBIC was, apart from its attractive styling, its modularity.

This enabled the use of standard products for approximately 95% of the enclosures with the result that only 5% of the design required new engineering.

It produced a very satisfactory cost-effective result".

One of Cranfield Aerospace's biggest tasks is that the company has to comply to a combination of both light and heavy industrial EMC regulations and invariably has to work to tight schedules.

This, in turn, means that its engineers only get one shot at passing the authorised EMC test procedures and for this SRS Products has been able to help and provide reassurance by carrying out many of the e.m.c.

testing prior to the official testing.

On this point, Martin Deards Managing Director of SRS Products PLC comments "EMC/RFI testing for enclosures raises a number of interesting points for manufacturers such as ourselves.

We never know what is going inside our cabinets, and, though we design our enclosures to the tightest of specifications, we cannot say categorically that everything will pass authorised testing.

Therefore, we have established our own test procedures and test equipment in advance ourselves and advise our customers with an infinitely greater degree of conviction.

This approach has been particularly useful with the Cranfield Aerospace project".

Cranfield Aerospace still manufactures by far the vast majority of the component parts, machining all the mechanical parts and on the electronics side, designs and assembles right down to PCB level.

But, the company is attempting to move away from this situation to sourcing outside.

The collaboration with SRS Products is essentially the first venture in this move towards the use of more outside contractors.

With the fixed-based simulator design, the aim is to trick the pilot into thinking he is having G forces applied to him.

This is achieved through four-axis motion control.

A seat height-module changes the eye height and gives vertical pitch accelerations cue together with up/down position adjustment and vibration/buffeting.

A lateral module provides backpressure lateral or sway changes.

The fore/aft module gives backpressure changes due to longitudinal G and provides surge acceleration cue.

The cushion module offers hardness changes due to vertical pitch acceleration cue together with shoulder harness and lapstrap tensioning to offer the pilot the negative G cues.

Thus, the pilots feel the illusion of G forces applied to them, the sensation of movement, with the impression of being forced out of or pushed back into the seat and of being buffeted.

The pilots also experience such things as runway rumble and the vibration off the tyres.

In fact, the complete effects of piloting an aircraft are simulated.

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