Geoffrey Sinclair
Staff Sergeant
- 927
- Sep 30, 2021
Roger Freeman Mighty Eighth War Manual. The 8th Air Force at least preferred British spark plugs. Aircraft Fuels section
All 8th Air Force tactical aircraft operated on special high octane fuel rated on a performance number scale as 100/130. They use of an inferior anti-knock value fuel in high performance engines would have resulted in overheating, detonation and pre-ignition, all causing engine damage. The 100/130 fuel was also used by the RAF and all aviation fuel supplies in the UK were the responsibility of the British. While 8th Air Force bombers were fuelled with 100/130 throughout hostilities, early in 1944 there was interest in the possible use of grade 100/150 fuel which would permit the use of higher war emergency power in fighters. In March, selected fighter squadrons tested this new grade, the results indicating that while the fuel permitted more power to be drawn from engines, it caused increased maintenance, primarily through persistent sparking plug fouling. Despite reservations in some quarters, all 8th Air Force fighter groups went over to 100/150 fuel between July and late September 1944. Attempts to reduce plug fouling by decreasing valve settings and adjustment of carburettor enrichment valves did not appear to help matters. During the autumn there was an alarming increase in the number of P-51 take-off crashes due to engine failure, mostly attributed to use of the 'Purple Passion' fuel.
Wright Field recommended the addition of ethylene di-bromide fluid with 100/150 to prevent fouling problems and in December 1944 the 355th Group was given the task of testing this grade, known as 'Pep'. By mid-January the trial was satisfactorily completed but British agencies were not so enthusiastic, their tests indicating that the additive in the fuel caused engine damage. On 8 February 1945 Technical Services reviewed the 355th Group experience, noting that no chamber corrosion or valve distortion had been found and that no field maintenance on valves had been necessary. Further the 'Pep' had appreciably reduced engine maintenances because plug fouling was practically eliminated. Other gains noticed were: reduction to a minimum of abortive sorties engine roughness, increased range, and less brake wear as the P-51s were able to taxi at lower rpm. It was felt that any extra wear on the valves or other engine parts was due to the higher power and not the 'Pep' fuel. As a result, 'Pep' 100/150, was being supplied to all fighter groups by March. However, contrary to Technical Services findings, fighter groups reported that while sparking plug life was prolonged, valve adjustment had simultaneously become a problem, checks having to be made every third or fourth mission instead of the usual 50 hours. Opinions differed but the most likely reason was thought valve seat inserts burning out, leading to diminishing .valve clearance and loss of power. Enthusiasm for the new fuel waned quickly and in the same month some units requested a return to 100/130. As the old grade had been largely replaced by 100/150, supply was difficult. By April the position with 'Pep' was so critical that a valve check was advised after every 25 hours flight. In the middle of the month a message to Wright Field requested valve seat inserts on V-1650 engines be made of stelite or other suitable material with corrosion resistant properties. It was found that there was additive separation when fed to the engine, forming hydrobromic acid which attacked the valve seats. In May the British had made a decision to supply 100/150 containing less ethylene dibromide as additional sparking plug maintenance was preferred to short engine life, a decision with which 8th Air Force concurred.
At this time the British were experimenting with 130/170 grade containing acetylene tetrabromide which they believed would make a more homogeneous mixture.
Spitfire XVI production
RAF Squadrons by C G Jefford, Spitfire XVI users. Sorted by start date and squadron, there was usually a change over period from old to new aircraft type.
All 8th Air Force tactical aircraft operated on special high octane fuel rated on a performance number scale as 100/130. They use of an inferior anti-knock value fuel in high performance engines would have resulted in overheating, detonation and pre-ignition, all causing engine damage. The 100/130 fuel was also used by the RAF and all aviation fuel supplies in the UK were the responsibility of the British. While 8th Air Force bombers were fuelled with 100/130 throughout hostilities, early in 1944 there was interest in the possible use of grade 100/150 fuel which would permit the use of higher war emergency power in fighters. In March, selected fighter squadrons tested this new grade, the results indicating that while the fuel permitted more power to be drawn from engines, it caused increased maintenance, primarily through persistent sparking plug fouling. Despite reservations in some quarters, all 8th Air Force fighter groups went over to 100/150 fuel between July and late September 1944. Attempts to reduce plug fouling by decreasing valve settings and adjustment of carburettor enrichment valves did not appear to help matters. During the autumn there was an alarming increase in the number of P-51 take-off crashes due to engine failure, mostly attributed to use of the 'Purple Passion' fuel.
Wright Field recommended the addition of ethylene di-bromide fluid with 100/150 to prevent fouling problems and in December 1944 the 355th Group was given the task of testing this grade, known as 'Pep'. By mid-January the trial was satisfactorily completed but British agencies were not so enthusiastic, their tests indicating that the additive in the fuel caused engine damage. On 8 February 1945 Technical Services reviewed the 355th Group experience, noting that no chamber corrosion or valve distortion had been found and that no field maintenance on valves had been necessary. Further the 'Pep' had appreciably reduced engine maintenances because plug fouling was practically eliminated. Other gains noticed were: reduction to a minimum of abortive sorties engine roughness, increased range, and less brake wear as the P-51s were able to taxi at lower rpm. It was felt that any extra wear on the valves or other engine parts was due to the higher power and not the 'Pep' fuel. As a result, 'Pep' 100/150, was being supplied to all fighter groups by March. However, contrary to Technical Services findings, fighter groups reported that while sparking plug life was prolonged, valve adjustment had simultaneously become a problem, checks having to be made every third or fourth mission instead of the usual 50 hours. Opinions differed but the most likely reason was thought valve seat inserts burning out, leading to diminishing .valve clearance and loss of power. Enthusiasm for the new fuel waned quickly and in the same month some units requested a return to 100/130. As the old grade had been largely replaced by 100/150, supply was difficult. By April the position with 'Pep' was so critical that a valve check was advised after every 25 hours flight. In the middle of the month a message to Wright Field requested valve seat inserts on V-1650 engines be made of stelite or other suitable material with corrosion resistant properties. It was found that there was additive separation when fed to the engine, forming hydrobromic acid which attacked the valve seats. In May the British had made a decision to supply 100/150 containing less ethylene dibromide as additional sparking plug maintenance was preferred to short engine life, a decision with which 8th Air Force concurred.
At this time the British were experimenting with 130/170 grade containing acetylene tetrabromide which they believed would make a more homogeneous mixture.
Spitfire XVI production
Month | No. | Cumulative |
Jul-44 | 1 | 1 |
Aug-44 | ||
Sep-44 | 9 | 10 |
Oct-44 | 181 | 191 |
Nov-44 | 94 | 285 |
Dec-44 | 64 | 349 |
Jan-45 | 117 | 466 |
Feb-45 | 108 | 574 |
Mar-45 | 121 | 695 |
Apr-45 | 65 | 760 |
May-45 | 51 | 811 |
Jun-45 | 108 | 919 |
Jul-45 | 74 | 993 |
Aug-45 | 59 | 1052 |
Sep-45 | 2 | 1054 |
RAF Squadrons by C G Jefford, Spitfire XVI users. Sorted by start date and squadron, there was usually a change over period from old to new aircraft type.
Sqn | From | To | Note |
402 | Aug-44 | Jun-45 | |
412 | Sep-44 | May-45 | |
66 | Nov-44 | Apr-45 | Also Sep 46 to Mar 47 as 164 sqn became 66 sqn |
127 | Nov-44 | Apr-45 | |
322 | Nov-44 | Oct-45 | |
453 | Nov-44 | Jun-45 | |
602 | Nov-44 | May-45 | |
229 | Dec-44 | Jan-45 | |
403 | Dec-44 | Jul-45 | |
416 | Dec-44 | Sep-45 | |
421 | Dec-44 | Jul-45 | |
302 | Jan-45 | Dec-46 | |
443 | Jan-45 | Jan-46 | |
451 | Jan-45 | Jun-45 | |
603 | Jan-45 | Aug-45 | ex 229 sqn |
303 | Feb-45 | Apr-45 | |
329 | Feb-45 | Apr-45 | |
340 | Feb-45 | Nov-45 | |
341 | Feb-45 | Nov-45 | |
74 | Mar-45 | May-45 | |
308 | Mar-45 | Dec-46 | |
345 | Apr-45 | Nov-45 | |
164 | May-45 | Sep-46 | |
317 | May-45 | Dec-46 | |
349 | May-45 | Oct-46 | |
401 | May-45 | Jun-45 | |
411 | May-45 | May-45 | |
577 | Jun-45 | Jun-46 | Target tow |
567 | Jul-45 | Jun-46 | Target tow |
587 | Jul-45 | Jun-46 | Target tow |
667 | Jul-45 | Dec-45 | Target tow |
695 | Jul-45 | Feb-49 | Target tow |
287 | Aug-45 | Jun-46 | |
631 | Aug-45 | Feb-49 | Target tow |
691 | Aug-45 | Feb-49 | Target tow |
16 | Sep-45 | Apr-46 | Ex 268 sqn |
595 | Sep-45 | Feb-49 | Target tow |
65 | Feb-46 | Oct-46 | |
126 | Feb-46 | Mar-46 | |
19 | Mar-46 | Nov-46 | |
350 | Aug-46 | Oct-46 | |
63 | Sep-46 | May-48 | ex 164 sqn |
501 | Oct-46 | May-49 | |
601 | Oct-46 | Jan-50 | |
604 | Oct-46 | May-50 | |
614 | Jan-47 | Nov-48 | |
609 | Apr-48 | Feb-51 | |
612 | Nov-48 | Jun-51 | |
5 | Feb-49 | Aug-51 | ex 595 sqn |
17 | Feb-49 | Mar-51 | ex 691 sqn |
20 | Feb-49 | Sep-51 | ex 631 sqn |
34 | Feb-49 | Mar-51 | ex 695 sqn |
31 | Mar-49 | May-54 | Communications sqn |
288 | Mar-53 | May-53 |