Classic engine power rating

[pauls640]

Hello everyone,

my first post here, I'm glad to enter this club . Maybe this has been discussed earlier in the forum, in that case forgive me. I have been wondering about the simulation of the calclassic aircraft. The tutorials available on the side explain how to operate the planes in classic times. But, as for me, I prefer to simulate them in the current times, which is overall realistic considering that there are many DC6, 7 and even a DC4 still flying. But nevertheless, the main issue here for a serious simmer is that the 130 - 150 avgas is no longer available, so the engine cannot deliver their "classic" power anymore. For example, the R-3350 are today limited to 52" MAP, I don't know about the others.

So I ask your advice on the matter about these engines, and I'd be very delighted to hear from FSAviator too, if he's available or interested in the matter.

Paul

[Maarten]

Hi Paul,

Welcome on the block.

The Pratt & Whitney Twin Wasp R-2000 series engines, (nowadays most used variants are R-2000-7M2 and Twin Wasp D5 (they are identical) delivering 1,450 hp MTO; C-54, DC-4, Carvair, Caribou, Hi-Per DC-3) are originally designed for 100/130 grade fuel. No problem for them to run on the currently available 100 avgas. Same for the Twin Wasp R-1830 series and the Wright R-1820 series (a.o. DC-3 and military versions).
The Pratt & Whitney Double Wasp R-2800 series engines flew on both 100/130 and 115/145 grade fuel. The engines mostly used on e.g. Convair 340/440 and the Douglas DC-6 series were the R-2800-CB16 (100/130) and R-2800-CB17 (115/145). The only difference between the CB16 and CB17 was the grade of fuel they were using at that very moment and the MTO power: CB16 2,400 hp, CB17 2,500 hp (according to the Airplane Flight Manual for the DC-6A/B I have and the book "R-2800" by Graham White). In fact last June I took a picture of an engine of Air Atlantiques DC-6B G-SIXC and its construction plate shows the engine type R2800 CB16 17. So basically no problem for the CB17 except for having to consume 100 avgas and behave like a CB16.

Indeed, the consequences for the R-3350 are more grave because they can't deliver the power they have been designed for due to lack of 115/145 grade fuel. I'll leave the details about those engines to one of my pals here. Too complicated for me to explain.

Have a good time here.

Cheers,
Maarten

[pauls640]

Thanks Maarten.

So suppose I'm flying a DC-6B with CB-16 engines, I'm still able to achieve TOGA power with ADI at 59" MAP on 100LL fuel?

Also, in my previous post I forgot to mention about the Wasp major mounted on the B377. Accordingly to the docs, the engine used by these planes is the R-4360-B6 variant. Now this one is rated 3500hp and can use 108/135 grade fuel. But since there are no strats flying today, it's probably silly to think about that ;D

Paul

[Maarten]

Yes. Nothing changed for the CB16.
I'm not sure how the Strats were coping with 100 avgas.

[Tom/CalClassic]

Hi,

Welcome!

A nice description of Avgas:

en.wikipedia.org/wiki/Avgas

Yep, as long as the engines used 100/130 gas, they can normally use 100LL. Many operators have reduced takeoff ratings for these engines too, but this is more commonly used to minimize the very expensive engine overhauls.

For engines requiring higher octane gas, operators normally reduced the takeoff, METO, and sometimes climb MAP values to avoid detonation.

There is a good site for looking at gas requirements, weights, fuel, etc. in US aircraft. Just search for the aircraft type (dc-6b for example) and then open the PDF.

www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/MainFrame?OpenFrameSet

Hope this helps,

[jesse]

On my MATS C-97G, using the R-4360-59 engines, we required as our primary fuel, 115/145. Our first alternate was 108/135 and our second alternate was 100/130 and 100LL. The dash one required a substantial reduction in all phases of power as indicate in the chart for Alternate fuel.

Jesse

[colorado]

Well organized info on current and historical aviation fuels, civil and military:

purvisbros.com/afi/index.htm

Jack

[volkerboehme]

Hi,

the R-3350 needed high-lead fuel much badder than the R-2800, and would have a considerably reduced power rating with low-quality fuels. This was one of the reasons why the Constallation series and the DC-7 series vanished from commercial use much earlier than the R-2800-powered DC-6 series.

Best regards,
Volker

[pauls640]

Thank you all for your valuable info, now I know how to stick to the (new) numbers.

Indeed, the limitations derived from low grade fuel are important on planes like the Connies and DC7's. They're not unbearable though, as I'm currently operating a DC7B on fsp with minimal profit loss.

On the other hand, it's obvious that in classic times, the difference between a "hampered" propliner and a jetliner was matchless.

[capflyer]

Most operators limit the R2800 to 50" MP even wet simply due to the lower cooling coefficient of 100LL. This has greatly increased the overhaul time on the engines (from somewhere in the range of every 200-300 hours to every 900-1000 hours). They also typically run only an 1100 HP cruise power instead of the more typical "prime year" 1600 HP, but that is a lot due to the fact that the aircraft are no longer operating at altitude and thus no longer using pressurization or the "high" blower setting. In fact, many operators have deactivated the "high" blower setting (all you have to do is unplug the switches and occasionally put a CB3 without the 2 stage blower) since the aircraft will never reach the required altitude to require its use.

On the DC-3B I fly with, we're using 600 HP cruise, so basically if you fly it using the "Econ" settings in the checklists, you'll be flying it like the real ones are. It's a bit slower, but it's a bunch better on the engines.

[capflyer]

I can't comment on the R2000 or R3350 because the two I have had any experience with aren't exactly "stock" to the aircraft they're on. I've not had a chance to go through "Old '927" yet to see what they're using on the R2000s mounted on it. And when "Fifi" starts flying again, it'll be with a hybrid engine.

Here's the description of the new engine by Gary Austin -

The new engines will be a combination of two of the latest (and most reliable) 3350's. The engines will have (basic description here) the power section, blower section, and accessory section from the -26WD (Skyraider engine), and have the rotating assembly, nosecase, and cylinders from the -95W (from an AC-119 Gunship). This engine will essentially be a Rare Bear "Light" engine. It is built for 3,500 horsepower, but we will only run it at around the 2,400 horsepower range. That will give us 200 hp more per engine, which the airframe should absorb with no problem, but also gives us the luxury of having available horsepower, should we need it in an emergency.

And so far the FAA is VERY happy with our engine project. With the airplane being in Experimental Category, we're really able to do whatever we wish (within reason), but to have them on board is excellent. I've gone over my plans with them and they didn't have a single negative comment to make about it, other than asking why this hadn't been done sooner.

I'm not certain exactly what we're going to designate the engines as, but they'll likely be called the R-3350-B29, since they'll be custom built just for this airplane.

Anyway, I'm sure there'll be plenty of things we haven't thought of yet, but for over a year an a half, we've been working on this solution, so I'm confident that this is what will keep FIFI flying for years to come.

Gary was the Crew Chief for the CAF B-29/B-24 squadron until recently when he accepted the position of Director of Maintenance for the entire CAF. He is still handling some parts of the engine project, but the idea is pretty exciting. We're supposed to have the first engine in Midland sometime shortly after the first of the year and put about 100 hours on it using the engine test stand (fondly called "Testiclese") to ensure the reliability of the engine. Once that's done the hard work of finalizing the contract with the engine builders will begin so that we can get the full lot of engines built and hopefully hung in time for AirSho 2009 (Sept. 25-27, 2009).

[Tom/CalClassic]

Here's your reply from FSAviator:

Greetings Paul,

As has already been explained, most piston propliners still used for public transport, including cargo operations, have engines no more powerful than the R-2800-CB16/17 that suffer little penalty from use of 100/130 Octane. Crucially the R-2800 will tolerate use of high blower when 100/130 Octane is in use. The R-2800 was designed so long ago that even the final variants were designed around the assumption that most commercial users would not have access to what was then 'military grade' 115/145 octane fuel in most locations. Those who had access could quickly reconfigure the R-2800-CB16 engine as a CB17 so that it could produce extra power when using 115/145 Octane. My 'CB16' flight dynamics have the correct air file curves for 100/130 Octane whilst my 'CB17' flight dynamics have the correct curves for 115/145 Octane. I supply CB16 versus CB17 flight dynamics and matched handling notes for both the DC6B v DC6A and for the CV34 v CV44.

No CV24, M202 or M404 owners ever configured their R-2800 engines as CB17s to make use of 145 Octane and to the contrary many soon removed the high blowers from their CB16s turning them into R-2800-CB3s.

I have not, and do not intend to replicate dual capability for the R-3350 or R-4360 powered propliners. Too few remain in public transport service for reasons mentioned by others and which I will now attempt to illustrate in greater detail below. I will use this opportunity to address the issue of other 'restricted power' propliner cases and the wider history of the need to 'make do' with low octane fuels.

Aircraft and engine certification is highly specific to individual variants so when you say;

<<For example, the R-3350 are today limited to 52" MAP>>

That may be true for a particular variant of that engine, in a particular variant of a particular aeroplane, and as a condition of employment for a particular employee, in association with an aeroplane relegated to a particular non public transport role, but it is sure to be false as a generic statement.

Let's consider two specific cases, both relating to R-3350 public transport certification. Consider the DC-7 and the DC-7B.

Regardless of the sub variant of R-3350-DA engine employed use of anything less than 145 Octane AVGAS is simply not authorised in the DC-7. Nobody ever applied for such certification, potentially just because nobody was willing to pay for the trials. However the DC-7 may be powered by the R-3350-DA2 engine and that may be significant.

To the contrary the DC-7B does have a schedule for 130 Octane, but the DC-7B must be powered by the R-3350-DA4 or later EA series engines. Somebody (presumably Wright) paid for (only) those late production engines to be certificated for use with 130 Octane. I surmise that Wright had already done company trials which caused them not to apply for the R-3350-DA2 and therefore caused Douglas not to apply for the DC-7 to have authority to use 130 Octane.

For the DC-7B which can lawfully be powered only by R-3350-DA4 or later series engines;

Using 145 Octane TOGA rating at sea level is 3250bhp at 2900 RPM at 56.5 MAP

Using 130 Octane TOGA rating at sea level is 2880bhp at 2900 RPM at 51.0 MAP

The TOGA application limit falls from 120 seconds to 90 seconds (from throttle up). Much more importantly use of R-3350 high blower is forbidden when using less than 115/145 Octane. All the high blower ratings are lost. The high altitude envelope is lost and cruising velocity is consequently greatly restricted. Max gross is reduced to 117,900lbs or less and METO power is also reduced.

So what are the implications for MSFS users who seek realism?

The issues are in reality just the usual ones. No one can extract realism from flight dynamics, however good or bad, without handling notes which mandate the inputs that must be made during each phase of the flight, and the limits that must be observed. The issue is not primarily one of flight dynamics. If we reduce weight to 117,900lbs and apply 51 inches instead of 56.5 for take off we will obtain a 'somewhat realistic' simulation of revised max gross 130 octane take off in a DC-7B using my existing FD. However to have identical realism for both fuels we need to swap between FD created to be equally realistic with either fuel which is what I have provided for the DC6B/A and CV34/44 as CB16/17 specific releases.

However.......

a) In my standard DC7B FD blower switching is automated (our virtual FE decides when it is appropriate). We must restrict our operating altitude; or procure alternative FD with manual blower switching and take care not to switch to HI gear.

b) MSFS is limited by an air file design that is 20 years old. The air file requires authoring of very simplistic 'segmented curves'. Between the numerically restricted vertices of the segmented curves errors maximise because the straight line no longer approximates the true curve. The 'art' of FD authoring is deciding where 'realism' will maximise and where it will minimise; using simplified handling notes to direct the process, both during authoring of the air file, and then during subsequent use of the air file.

Consequently application of 56.5 MAP at 2900 RPM at SL in ISA will deliver very close to 3250bhp, but applying 51 MAP @ 2900 RPM will approximate 2880bhp much less closely. 51 MAP @ 2900 RPM will not co-incide with a vertex in my DC-7B R-3350-DA4 air file code because my code assumes 145 Octane.

The upper power curves for 145 and 130 octane are different and they are as different as writing two different sets of FD for two different engines. To have equal realism, when simulating 130 octane, DC7B FD specific to that case would need to be produced, with each air file vertex at the appropriate conjunction of MAP and RPM for 130 octane accompanied by handling notes directing the user to apply those specific real world conjunctions. Creating 130 octane FD and handling notes from 145 octane FD and handling notes requires about 50% of the time taken to produce the original 145 octane FD and handling notes. It is not just the take off case that differs.

For instance in the DC-7B;

Using 145 Octane METO rating at sea level is 2700bhp at 2600 RPM at 49.0 MAP

Using 130 Octane METO rating at sea level is 2380bhp at 2600 RPM at 41.5 MAP

Although I do not intend to produce 'reduced power' flight dynamics and handling notes for R-3350 or R-4360 powered aircraft I have already done so for all other 'relevant' engines. The situation for those is as follows.

Partly in order to illustrate that this issue is not a 'modern' issue my Goose handling notes address the issue of variable octane, because for 'bush planes' variable fuel quality away from 'airports' and anywhere in the 'underdeveloped world' has been an issue since the 1930s.

My Goose handling notes specify;

<<This aircraft may be operated using all or part 80 Octane AVGAS but during LOW OCTANE operation MAP must NEVER EXCEED 33.5 inches and RPM must NEVER EXCEED 2200 until fuel tanks have been drained and pure 87 Octane or better loaded. Do NOT use full fine screws for 80 Octane departure.>>

I included those low octane R-985 handling notes for the Goose because in the absence of high gear blowers it is that simple. TOGA time limit does not vary, METO does not vary, gross weight is not reduced, but take off run is extended. I doubt that my singular Goose FD for use with either octane fuel replicate the penalty of using 80 Octane fuel with any precision, (and certainly won't from over viscous MS water), but the issues can be confronted and the need to moderate both MAP and RPM realistically in relation to many older engines may be experienced.

Some of my propliner FD address 'relegation with age' and the change of role issue.

For instance the Canadair C-4 Argonaut handling notes specify;

***********************************
BOAC (launch customer) normal cruise:
BOOST = 5
RPM = 2350
Check RADIATORS < 100C
Plan 1800 PPH
Note: yields 256 KTAS at FL250
****************************
BMA (second hand user) normal cruise:
BOOST = 2.5
RPM = 2200
Check RADIATORS < 100C
Plan 1400 PPH
Note: yields 230 KTAS at FL250
****************************

Long haul scheduled flying in the 1950s and and medium haul inclusive tour work in the 1960s required different cost controls to maximise profit. Both airlines needed to use HI blower, but for different reasons. BOAC needed to market the high cruising velocity of the Argonaut to attract premium fare passengers, but were happy with low utilisation. BMA needed a single crew to make two rotations per day from the UK to the Mediterranean resorts. That required cruising velocities obtainable only in thin high air in order to deliver the necessary low fare seat miles per day from just one rostered crew. So both airlines used 145 octane fuel and employed similar techniques before and after cruise at high level, but by the 1960s inclusive tour propliners cruised no faster than was necessary to deliver the desired daily rotations within the daily crew hours limitations which were then subject only to union agreements and not to UK government regulation.

The 'restricted power' operating cases are fairly well catered for, but only if I deemed the 'restricted power' case to have had sufficient significance and usage in the real world to justify the extra work involved in creating two sets of flight dynamics and/or handling notes. Use of R-3350 and R-4360 engines with 130 octane fuel is, and always has been, abnormal, but for the R-2800 using 130 octane was always the norm in commercial service with 145 octane the norm in military service, so I created both sets of FD and both sets of handling notes for relevant versions of the R-2800. Older engines like the R-2000 derived no benefit from using 145 octane. For the Argonaut and the Goose I created only one set of FD and handling notes, but placed air file segmented curve vertices to deliver 'realistic' output at both relevant conjunctions, because that was possible for the R-985 and the Merlin.

Engines like the R-1830 used in the M130 and R-2600 used in the B314 have similar issues to the R-985, but PAA, BOAC and the USN were always supplied with the highest grade fuels and those boats never had to make do with low octane fuel, however that was defined at the time.

The wider picture is that 145 Octane was an oil superpower resource. Ditto for lower octane fuel timeframe by timeframe in aviation history. Only nations which were granted a favourable trading status were granted the right to buy 'military grade fuel' from an oil superpower. The need to make do with 'low' octane fuel is not modern, but for most of aviation history the reasons were different. Nations that were not abiding by restrictions imposed by an oil superpower on their internal and external political and trading behaviour often had to make do with aeroplanes and engines that could cope with 'low octane' fuel and they had to make do with the resulting restricted performance and consequences. Whether those aeroplanes were for combat or transport use.

Producing 'realistic' FD and handling notes for combat simulation is a nightmare. The following, although off topic here, may help to illustrate the complexity and how quickly things may change from a real world and MSFS user perspective.

The octane rating of fuel supply in the logistics chain has been a huge issue throughout the history of the piston aero engine. In the late 1930s France made the mistake of assuming that if it was allowed to import the latest American combat aircraft with engines that required high octane fuel to deliver TOGA and WEP the United States government would automatically allow US oil companies to supply it. They did not. The 'Boys Book of Wonderplanes' will tell us that the Curtiss P-36s of the French Air Force employed during the Battle of France had '1200hp engines' superior to the '1100hp engines' in the Bf-109E, but of course they did not. France could only produce 87 Octane fuel in its refineries and could not run the latest R-1820 Cyclone or R-1830 Twin Wasp engines at more than 1050hp (their METO rating). To produce TOGA or WEP both required 100 Octane and the US government withheld it.

RAF units based in France, for the defence of France in June 1940, were supplied by France, regardless of engine type and prior command structure. They all received only 87 Octane. A Hurricane I running on 87 Octane was limited to only its rated power of 1030hp (no WEP available), much less than a Bf-109E. After evacuation to RAF Biggin Hill and filled with UK or US refined 100 Octane the same engine could be overboosted to about 1225hp (WEP), much more than a Bf-109E, during the subsequent Battle of Britain.

For the poor old RAF Lysander pilot the situation was reversed. In the French Army logistics chain in the morning he received 87 Octane and could deploy 890hp WEP for five minutes, but on evacuation to RAF Gatwick, suddenly back in the British Army logistics chain he could obtain only 83 Octane in the afternoon and lost the ability to generate WEP and was restricted to TOGA power and only for TOGA duration. If realism is desired a move of less than 100 miles in a day involving a change of fuel supply invokes different MSFS flight dynamics, but especially requires different handling notes. Biggin Hill and Gatwick are a few minutes flying time apart, but it is the fuel available that matters and that may have little to do with the date of the simulation. The octane rating of fuel available is mostly about logistics and is highly relevant to simulation realism, (or any wider historical comparative evaluation of aircraft capability), at any date.

FSAviator.

[Tom/CalClassic]

Hi,

Another reply from FSAviator:

Brazil were forced to abandon their post colonial independence, become co-belligerent, and allow US basing rights during 1942. They qualified for U.S.produced military grade AVGAS by accepting the relevant U.S. ultimatum. By 1944 the Brazilian Air Force was operating its P-47s against the Luftwaffe in Europe using U.S. supplied 145 AVGAS. Brazil remained politically unstable and subject to periodic recession.

The U.S. bribed Thailand to abandon its ancient neutrality and join SEATO in 1954 as the French Empire lost control of Indo China to the Viet Minh. The Viet Minh already had substantial bases in Laos on the Thai border. The US donated 100 Bearcats and the 145 AVGAS they required so that the Thai Air Force could begin the bombing of Laos immediately. Thailand also had to agree to unlimited US basing rights so that the U.S. could step up the bombing of French Indo China as and when required. Thailand thus gained rights to 145 purchase, but Thailand also remained politically unstable and subject to recession.

It was Sweden that stubbornly remained neutral, refused the U.S. basing rights, and had no right to buy 145 AVGAS from US oil companies, but nations that joined NATO also had to agree to US basing rights so both Denmark and Norway gained access to 145 AVGAS from US oil companies in 1949. SAS thus had access to 145 AVGAS. Neutral Sweden had to spend much of its GDP buying British jet combat aircraft and developing early jet combat aircraft of its own powered by British jet engines and running on AVTUR which was available everywhere, because it could not obtain a reliable and sufficient supply of high octane AVGAS in the relevant era. The Swedish Air Force still operated the Ju-86 alongside the Saab Draken long after the air forces of Denmark, Brazil and Thailand had procured far superior transport aircraft. Even after introducing Mach 2 guided missile armed fighters Sweden could operate only the C-47. PBY and Ju-86 military transports because all could run on only 87 octane if necessary.

Regards,


FSAviator

[Maarten]

As a matter of fact the Swedish military C-47s and PBYs were equipped with Swedish wartime-built copies of the Pratt & Whitney Twin Wasp SC3G (civil name for the pre-war R-1830s). They were called Flygmotor STW C3 (STW=Svenske Twin Wasp) and were rated at 1,050 hp MTO power at 2,700 rpm (42" map). The STW C3 was originally built for the J 22 single-engined fighter, built by the Kungl. Flygförvaltningens Flygverkstad (translated something like Royal Aeroclub Aircraft Workshop), the SAAB 17A single-engined dive-bomber, and the SAAB 18A twin-engined light bomber. When these aircraft became obsolete, the engines were found suitable to power the Swedish Air Force's C-47s and PBYs.

Until the late 1980s - early 1990s one of these C-47s, by then operated by Flygande Veteraner (Flying Veterans), Stockholm-Bromma, as SE-CFP 'Daisy' ("Fridjof Viking"), still was equipped with STW C3 engines. I took photographs of the engines and their construction plates when the C-47 visited the Dutch Dakota Association. At some time the STW C3s had reached the end of their operational life, partially due to the fact that no spares were available and P&W spares could not be used because the Swedish engines had been built according to the metrical system. They were replaced by the original Pratt & Whitney R-1830-92s which delivered a bit more MTO power (1,200 hp).

Cheers,
Maarten