Other Packard Merlin powered aircraft?

[Geoffrey Sinclair]

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

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​

 

[MIflyer]

Do you have a source for the RAF crews modifying the Typhoon's Sabre for higher speed at lower altitudes?

Just something I read from Bill Gunston.

 

[BarnOwlLover]

There was a Fiat G61 that was a much modified G55/59 design that used the same Packard Merlins as the P-51 Mustang. It used a nose design and radiator design similar to the Merlin Mustangs mated to a G59 bubble canopy fuselage. Found on Secret Projects forum.

Probably abandoned as it was cheaper to buy P-51s and Spitfires as surplus from the USAAF and RAF than set up a new production line for a much modified World War II design.

 

[MIflyer]

There was a Fiat G61 that was a much modified G55/59 design that used the same Packard Merlins as the P-51 Mustang. I

The Italians did something unusual after WWII. They designed and built a 12 cylinder in-line engine intended to replace WWII vintage Allison and Merlins, under the theory that the aircraft that used them would be in service for many more years and that RR and Allison would not keep producing those engines, having moved on to later designs and jets. I suspect that the available surplus engines killed that idea. Note that while the Merlin was built in a transport version intended for the Canadian version of the DC-4, for the most part WWII aircraft like Lancs and Mossies were being scrapped and the engines saved and that process went on for years. The French Fennec attack version of the T-28 used R-1820 engines from B-17G's. A friend of mine worked for an oil company in OK and he said that they bought surplus V-1710's for use as oilfield power plants before realizing that they were not well suited for that purpose.

 

[GrauGeist]

Growing up in Southern California, we had oil fields all over, including rare wooden derricks and wooden beam equipped rockers. By and large, the engines driving the pumps were inline six cylinders of various makes.

 

[Reluctant Poster]

A book about Canadian units indicated the Merlins in the Mk XVI proved to be rather less reliable.

A college professor I knew flew P-51's in WWII. He said that there was noticeably lower vibration with RR Merlins than with Packards, which he attributed to the RR craftsman approach of selecting pistons individually so that they all weighed as close to the same as possible.

The Packard approach would be more oriented to making sure that the pistons had a lower variation in weight when produced, ala Deming.

Note that there was a huge difference between the V-1710 and the V-1650 when it came to field maintenance. The Merlin had a single piece block. The Allison's gearcase and accessory sections could be removed and the engine could even be converted between right hand and left handed rotation in the field.

When the USAF got the Allison TF-41 version of the RR Spey they ignored the fact that the engine was designed to be built up individually, with assemblies match drilled rather than just assembled out of a bin or parts. Taking the engine apart for overhaul and distributing the parts for cleaning, inspection, and repair without trying to maintain serial number integrity did not yield good results. When I was sent to Myrtle Beach AFB in October 1975 to get their A-7D's back in the air they had 80 airplanes but only 37 engines; OC-ALC was unable to deliver enough engines . The need for frequent engine inspections had resulted in the field units inventing a labor saving approach that resulted in creating the problem I was sent to fix.

As I have posted previously Packard weighed their pistons. In fact even Ford weighEd their pistons for their production cars. I posted a video showing Ford doing that.

 

[Howard Gibson]

A college professor I knew flew P-51's in WWII. He said that there was noticeably lower vibration with RR Merlins than with Packards, which he attributed to the RR craftsman approach of selecting pistons individually so that they all weighed as close to the same as possible.

Did Rolls Royce Merlins reach service in Mustangs?

 

[GrauGeist]

Did Rolls Royce Merlins reach service in Mustangs?

Only five, the Mustang Mk.X, which were used for testing and none saw combat.

The the Australian Mustang, CA-18 Mk.23, was also fitted with the Merlin.

 

[Engineman]

I also read that when the P-51B first started flying in the ETO the USAAF found out the hard way that the stock spark plugs they had on hand did not work well in the V-1650 engine, as in Very Much Not Very Well. Engine failure would occur NLT maybe 20 hours. I read of one guy who even had to splash down in a French river on one of his first flights, with only a few hours on the airplane. Now that would be a pisser! Did the V-1650-3 need spark plugs the RAF had but the USAAF did not? Were they using plugs that had been meant for the P-47 or P-38? Or was it that the Spit XVI was fitted with V-1650 when built and no one thought to swap out the installed plugs at Castle Bromwich with the good ones?

Hi, I am coming in here late I'm afraid. It seem's that UK/USA Sparkplugs were always in a bit of a to-and-fro development cycle. Back before 1939, there were still many sparkplugs with Mica insulation. The big improvements started with the development of ceramic or sintered insulator with precious metal fine-wire electrodes. Certainly Rod Banks writes of bringing early ones back from Germany in the late 1930's. However, for Germany that was the best they got because they could not continue with precious metal fine electrodes as they had limited resources. In addition, the Germans had great problems with their further sparkplug technology and were always a weakpoint during the War.
The UK/USA story seems to go forward with sparkplug development that was much better than the German's. However, as engines developed with higher Manifold and Boost pressures, combined with more exotic fuels, sparkplug problems kept appearing and being solved. It certainly seems that there were particular times when there were shortages of particularly good sparkplugs as new aircraft/engines came into use and there seems to have been certain difficulties and arrangements that favoured certain units at times. Overall, it seems that there was good co-operation but, I can imagine the bad feelings if any units sensed that they were being left out.

Eng

 

[Shortround6]

As I have posted previously Packard weighed their pistons. In fact even Ford weighEd their pistons for their production cars. I posted a video showing Ford doing that.

Unless somebody can post spec sheets or overhaul instructions showing the actual weights used or allowed I agree with you that this should be retired.

See item 30 in the list, This is listing for overhaul tolerances.
This is for a Merlin II engine from a 1942 book. Now can somebody show that the Packard engines were assembled using different tolerances?
The Packard parts were supposed to be interchangeable.

Also note that not only is there a specification for the pistons, there is a specification for any two pairs of pistons, piston rod assemblies.


Book is "Aircraft Handbook" by Fred Colvin.

 

[Reluctant Poster]

I wonder about that, since if they were using the same engines from the same source as those for the P-51, WTF? Did the RCAF crews modify them for higher speed at lower altitudes, like some RAF crews did with the Typhoon's Sabre, with disastrous results?

I also read that when the P-51B first started flying in the ETO the USAAF found out the hard way that the stock spark plugs they had on hand did not work well in the V-1650 engine, as in Very Much Not Very Well. Engine failure would occur NLT maybe 20 hours. I read of one guy who even had to splash down in a French river on one of his first flights, with only a few hours on the airplane. Now that would be a pisser! Did the V-1650-3 need spark plugs the RAF had but the USAAF did not? Were they using plugs that had been meant for the P-47 or P-38? Or was it that the Spit XVI was fitted with V-1650 when built and no one thought to swap out the installed plugs at Castle Bromwich with the good ones?

I posted on the inferiority of American spark plugs previously;

F4U vs F6F & Top-Speed: Let's Settle This

The British didn't have the same problems. They had better spark plugs which were less susceptible. From the Fedden Mission Report that I posted recently: According to the book "The Vital Spark" the British used ceramic in lieu of mica for the insulator and platinum for the electrode. The...

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