top of page


ML 12P Mk. 4G

During 1961, Swiss AF evaluations for a new high-performance aircraft were underway, and the purchase of high-altitude pilot equipment for intercepts above 15,000 meters (50,000 ft) was being assessed. 

Since the Mirage III was the lead aircraft in the evaluation, together with the aircraft manufacturer, GAMD (Générale aéronautique Marcel Dassault) and the Brétigny CEV (Centre d'Essais en Vol), assessments regarding the ARZ (Aerazur) 30 partial pressure suit and the EFA (Etudes et Fabrications Aeronautiques) Type-12 helmet were underway.

However, in a note dated September 12, 1961, H.Häfliger, KTA (Kriegstechnische Abteilung/Technical War Department) pilot, returning from his visit to the SBAC Farnborough Airshow reported that he had had the opportunity to see a British partial pressure high altitude helmet, the ML-12. The ML Aviation Company Ltd.,located at White Waltham Aerodrome, Maidenhead, Berkshire took the initials of its founder, Sir Noel Mobbs and its technical director, Belgian born Marcel Lobelle. 

Of this helmet he mentioned the pros:

No hold down harness necessary for its use;

The pilot could fly with the visor open, in the event of decompression this would close automatically;

A sun visor integrated into the helmet;

Being fitted with an oxygen mask, the possibility of inhaling stale air reduced to a minimum;

Provided with an opening allowing to talk to other people or drink;

According to the manufacturer, the helmet customizable to French and American pressure suit configurations;

Compatible with the Martin Baker Mk.4 (Mirage III) seat;

The helmet already selected by the German and Canadian AF and under evaluation by the Dutch Air Force.

Consequently, he recommended the purchase of two specimens to be tested with the ARZ suit.

The proposal was accepted and in May 1962, the KTA ordered and was provided with a specimen of the helmet on loan  (to be returned by the end of October 1963), identified by the ML company as

"Type 12 P, Mk.4 S" prototype. The same was made available to the FAI (Fliegerärztliche Institut/ Aeromedical Center) for the required tests.

As mentioned above the helmet was considered to be a prototype, according to the manufacturer the differences to the RAF configured model were as follows:


The helmet fitted with 1/2 inch (12.7mm) bore hose connected to a metal valve body. The arrangement suitable for an injector type oxygen regulator, such as the Bendix system fitted to the Lockeed F-104C.

Oxygen mask microphone - impedance 7.0 ohm; headphones - impedance per pair 9.0 ohm. The arrangement compatible with the USAF AIC-10 system in use by NATO.

Comm cable fitted with the RAF (NATO) standard jack-in plug.

No visor heating as the double layer (air-space) visor deemed sufficient for the possible relatively short emergency duration , as per planned test flights. 

Ejection automatic "g" activated visor closure system not active/ not fitted as specifically intended for the Lockeed C-2 seat without face blind.

The FAI requested the KTA to carry out flight tests on board a DH-115 Vampire T.55, limited to an altitude of 3000 meters (10,000ft) with the not flying pilot wearing the ML 12 not connected to oxygen and radio systems, asking the following questions: 

- With increasing g's, is there a tilting tendency in any direction?

- Up to what number of g's (max 6) can you straighten up your head?

- With variable manoeuvres and g's, is it always possible to turn the            head in the desired direction?

- Is the weight of the helmet tolerable throughout the mission?

- Is the field of vision sufficient?

- Is the optical quality of the clear visor sufficient?

- Is the quality of the dark/anti glare visor sufficient?

- There is a tendency to heat build up?


The tests were limited to a single flight in October 1962; on ground the ML 12 was evaluated inside the cockpit of a Mirage. 
In the meantime, in September 1962 during a trip of KTA pilots to GAMD in Paris, the EFA T-21 was introduced, featuring a bearing-mounted head rotation system. 
The final ML 12 assessment reported the following:

- The helmet to be heavier than the previously tested EFA Type 12, USAF MA-2 and the "new" EFA T-21;
- With limited sideways movements capability (in the Mirage cockpit),
- When closing the canopy, the handle bar of the visor sometimes coming in contact with the glass, causing the visor to snap shut; 
- The lower part of the helmet (mask, padding and frame) to be too bulky, obstructing the view of the lower part of the cockpit.
- The fact of being able to fly with the visor open, not a sufficient compensation for the above problems.

As a result of this evaluation, the ML 12 was not considered suitable for use by the Swiss AF Mirage III crews. 

The helmet was supplied in two sizes, 1 (small) and 2 (large); the suffix after the Mark Nr. as "G" or "S" denoting configuration changes/ deviations from the standard one as required by the various Air Forces.


Is interesting to know that the ML 12 was the helmet worn by test pilot Brian Trubshaw on the day he piloted Concorde 002 on its first ever flight from Filton in Bristol.  

Our specimen is a "G" model dating from 1966.


The helmet box contains: One Helmet ( Mark as specified); a spare helmet liner; 2 spare pads; a visor cover; Lissapol in bottle; talc in bottle; 1 yard of 4in. x 2in. of Flanelette and a descriptive, instruction and servicing manual.    

bottom of page