The Sutton Harness on the Spitfire

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“The first thing I felt was the thud of bullets hitting my aircraft and a long line of tracer bullets streaming out ahead of ...

“The first thing I felt was the thud of bullets hitting my aircraft and a long line of tracer bullets streaming out ahead of my Spitfire. In a reflex action I slammed the stick forward as far as it would go. For a brief second my Spitfire stood on its nose and I was looking straight down at Mother Earth, thousands of feet below. Thank God my Sutton harness was good and tight. I could feel the straps biting into my flesh as I entered the vertical with airspeed building up alarmingly. I felt fear mounting. Sweating, mouth dry and near panic. No ammo and an attacker right on my tail.”
Flt/Lt Dennis N. Robinson, No. 152 Squadron

The actual ditching was a tremendous thump. The aircraft must have been travelling at over 300 m.p.h. and the deceleration pressed me against my Sutton harness with tremendous force. The aircraft immediately sank and water poured in. I remember swallowing water but do not recollect being thrown against any part of the aircraft and being injured. At the time, to release my harness I had great difficulty in pulling the pin because it had been bent in the deceleration process. As I struggled, I felt the pressure of water getting greater and greater as I went down with the aircraft. Eventually I got free and shot to the surface. ”
W/O Jim Haugh, No. 464 Squadron RAAF

The seat belts used on the Spitfire and other British aircraft of the era are often being referred to as the Sutton Harness. What exactly was the Sutton Harness?

The Sutton Harness used in single-seat fighters was a patented quick-release safety belt system introduced late during World War I. Over the years, several types of Sutton Harness were developed, covering both simple lap straps and four-point aerobatic harnesses. In the 1930s, the four-point Sutton harness was a broadly established standard in all RAF aircraft types, from de Havilland DH 82 Tiger Moth and Miles Magister to the Spitfire and Hurricane.

Sutton Harness

The Sutton Harness system in the Spitfire
[Crown Copyright]

The Sutton harness commonly used during the initial to mid-war period consisted of four straps about 2” wide that had a row of grommets spaced about 1and 1/2 ” apart.

The shoulder straps of the harness were attached at a single point to a transverse cable which was attached by brackets bolted to the ends of the fuselage longerons behind the pilot’s head/shoulders. The length of the cable provided a degree of shock absorption upon impact. Also, the wire could be slackened by means of a lever in the cockpit to permit the pilot to lean forwards.

The lap straps were attached to the lower airframe.

The four straps met in front of the pilot’s chest. On the free end of one of the lap straps there was a brass locking cone that had a hole near the top that passed laterally through the cone for the locking pin. The pilot put the remaining three straps over the cone and locked the straps together in the pilots lap. The distinctive-looking locking pin was secured to the cone strap with a leather thong.

Shoulder straps of the Sutton Harness
[Crown Copyright]

When the pilot wanted to release himself, he pulled on the thong which withdrew the locking pin from the cone, freeing all straps simultaneously. It was the first quick release device.

Due to the way the shoulder harness was attached to the fuselage structure, the part of the harness going through the armoured bulkhead behind the seat and continuing to to the rear was one of the clearly visible thingies inside the rear glazing of the Spitfire (and sadly, is one thing regularly overlooked by modellers).

The attachment cable of the Sutton harness visible under the rear glazing of the Spitfire.

The upper buckles are threaded through frame 11 (behind pilot) referred above and bolted to a bayonet coupling, connecting the shoulder straps to two wires going back over the antenna mounting frame, one each side of the mast foot, to an anchor point at frame 15. Another wire attached the bayonet coupling to the longitudinal frame under the rear glazing, probably to prevent the coupling from disappearing down into the fuselage when the straps were unfastened. The Y-shaped end of the shoulder straps went down behind the seat back, toward an anchor point on the seat mounting frame. 

Type QK Harness

Around 1943, the revised Type QK harness was introduced as RAF standard, similar in configuration but attached directly to the reinforced seat frame rather reaching back to the fuselage frame no. 15.

This photograph illustrates how the pilot was strapped in the Sutton Harness. The locking pin was attached by a thread to one of the shoulder strap, and is often seen hanging along with the strap over the cockpit sill and down the fuselage side of aircraft on readiness. The pilot is Norwegian Kjell L’Abbee-Lund while serving with No. 611 Squadron.

Type QS Harness

In 1946 came another modification, this time in the form of Type QS harness. It was generally similar in operation but rather than relying on reinforced grommets for length adjustment, the straps could be tightened through locking buckles, and so the two chest and one lap straps ended in metal lugs which could be locked into a circular quick release box mounted on the remaining lap strap. This harness moved the lap straps backwards, to the rear corners of the seat, bringing them over the pilot’s hips, and doing away, completely, with the “Y” strap behind the pilot.

Type QS harness as mounted in post-war Spitfire Mk. XIX.
[Martin Waligorski]

Both the French and the Germans developed similar quick-release systems. The French also had a release box affixed to one of the lap straps, with the other three straps having metal lugs that inserted into the box. Turning the knob released the straps freeing the pilot. The standard Luftwaffe harness was similar in its function to the Sutton harness.

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By Edgar Brooks  |  2014-10-19 at 18:24  |  permalink

The harness was much more complicated than that. The first “ordinary” Sutton harnesses were the “M” & “K”, which had thigh straps which attached to the seat frame; there is a life-size drawing of the “M” in the National Archives at Kew.
It’s likely that the difference between the “M” & “K” concerned the straps, since Dowding had to ask for longer straps when seat armour was introduced, so the “K” seems to have followed the “M.”
. The “QK” was a derivative of the “K,” but had the thigh straps moved back to the corners of the seat, so that they came over the pilot’s hips; this also needed a strengthened seat, so it’s impossible to say which airframes had them, but it seems to have been 1944 before it came into service.
Next was the “QL,” which was not a Sutton, but had a parachute-style of quick-release box; it was used on the XVI, in 1945, and the shoulder straps were attached directly to a bracket on the pilot’s head armour. It was also intended for the F.R.XIV which was to have a fuselage fuel tank behind the pilot.
The “QS” was next, which was also a “parachute-box” type, but was used on standard fuselages (without extra fuel,) so that the old-style Sutton-type release mechanism could be retained. It only appeared post-war (about mid-1946.)
Last was the “ZB,” which was like a modified “QL.” It had just the four straps, but the shoulder straps ran through a bracket, behind the pilot’s neck, then down to the old-style release mechanism of the early Suttons. This enabled the behind-pilot fuel tank to reappear, in the late-Mark versions.

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