The Engine That Could

“Don’t make ’em like they used to…”

I’m not sure if it was a question or a statement, but the docent who sidled up to my son and I recently at the Museum of Flight was right as rain. We stood silently for a few moments, gazing at the long lines of the warbird fuselage in front of us.

I’d already read Airscape Magazine’s two-part series on the developmental history of the Supermarine Spitfire (nerd alert!), so perhaps it was a father-like-son moment which prompted my two year old to make a bee-line for the Spitfire Mk.IX when we entered the museum’s Personal Courage Wing.

The plane itself received a once-over. But what really caught my kid’s attention was the Rolls Royce Merlin engine parked nearby. It was accompanied by an informational display and panel with a single button. I dunno if the kid is going to be a pilot when he grows up, but if one of the signs is a love of pressing buttons, the odds are looking good. This one played a throaty recording of a Merlin starting up, followed by the sound of a high-speed fly-by of a Merlin-powered Spitfire.

Rolls-Royce Merlin engine

He must have pressed that button a hundred times. There’s something universally captivating about the sound of a large-displacement inline engine and propeller going by at hundreds of miles per hour. Even a two year old gets it.

Although some Spitfire variants were propelled by Griffon engines, the majority of the 20,000+ fleet rolled off the production line with the slightly smaller Merlin powerplant.

Now, I’m a big Rolls-Royce fan. Not because of their automobiles, which is what most Americans probably associate them with — to be honest, I probably wouldn’t know one of their cars if it parked in my driveway and I was handed the keys. No, it’s because the planes I fly at work are powered by Rolls-Royce engines.

In fact, every true Gulfstream aircraft thus far has been paired with a Rolls-Royce engine. The original Gulfstream turboprop utilized a Dart 529. The G-II and G-III were paired with Spey turbofans. My G-IV has Tay 611s. The G-V/550 is powered by the BR-700 series. The flagship G650 travels with one of the latest Rolls-Royce engines, the BR-725.

This line of turbofans is famous for a long history of power and reliability. I think of it as the jet equivalent of Pratt & Whitney’s PT6A turboprop engine. It just goes and goes. Interestingly, Gulfstream recently broke with tradition and selected Pratt’s PurePower PW800 series for the upcoming G500 and G600 aircraft, so the long romance between Savannah and Britain may be coming to an end. If so, the pairing will still go down in history as one of the most successful in aviation history.

Anyway, those Merlin/Griffon reciprocating engines were a huge success for Rolls, and even today they remain among the most iconic elements of classic warbird aviation. Of course, the war only lasted a few years, and it seems piston technology was barely mature before everyone was racing to cast it all aside in favor of turbojets.

Rolls-Royce started working on a replacement for their aviation recips even before World War II ended, and this jet engine aspiration became the known as the Avon. This moniker might bring to mind the billion-dollar direct sale cosmetics company; thankfully, there’s no relation whatsoever. Like many of Roll’s engines, the Avon was named after a British river. Although I’m not sure which one. “Avon” is derived from Celtic word for “river”, and at least five waterways in the United Kingdom share that name.

The Avon turbojet engine was first run in 1946, and and the last one was produced… well, that’s the kicker: they never stopped making them. Though they’re not produced in large numbers, as far as I know you can still get a new one today.

An early Avon engine

Conventional wisdom would suggest avoiding the first product of any new technology. Lord knows the first “laptop” computer, automatic transmission, or cellular phone was no prize. Yet here’s one which has been powering aircraft, ships, factories, drilling rigs, and just about anything else for nearly two-thirds of a century. To be sure, Rolls has made improvements and upgrades to the line, but still, what an impressive record.

And speaking of records, according to a Wikipedia page on the Avon, in 1982 one of these engines ran for 53,000 hours before requiring a major overhaul; in ’94 one operated continuously for 476 days. To put that into perspective, the Tay 611 engine on my Gulfstream IV-SP — which is about four decades newer than the Avon — is opened up for a hot section inspection every 4,000 hours and is totally disassembled for a major overhaul every 8,000 hours.

That’s not to say a Tay couldn’t do everything an Avon does. I’m sure it could. Industrial uses are nowhere near as critical as aviation applications — that’s why the overhaul and inspection intervals for aircraft engines are so much shorter than the astronomical numbers posted by the older design. Still, it’s a unique testament to British aviation in general, and Rolls-Royce in particular, that an engine can remain in profitable production for so long.

Will any of the designs on today’s drawing boards still be in production 70 years from now? Probably not. A fellow pilot recently mentioned that his employer is in the process of trading their existing G450 for one of upcoming fly-by-wire G600s. Their question to the CEO of Gulfstream was aircraft longevity and how long they plan on supporting their aircraft. The answer was surprising. While they do support everything out there, all the way back to the original turboprop-powered Gulfstream I, they plan a ten year cycle on their current aircraft.

  16 comments for “The Engine That Could

  1. Hannah
    April 20, 2017 at 8:32 am

    That’s really adorable about your son! You’re raising him right! 😀 And I do think that pushing buttons could be that sign of a future pilot.

    So, do you think that prop planes will ever make a major comeback? Or do you think that jets will continue to monopolize comercial aviation?

    • April 20, 2017 at 10:37 am

      Props will probably remain the most efficient option for slower, low-altitue flying, so I foresee their continued presence for training, light general aviation, bush flying, very short hops, drones/UAVs, and so on. But for most commercial applications the turbojet will reign supreme due to their reliability and power output. Reciprocating and turboprop engines are simply not reliable or efficient enough, respectively, for those uses.

      Turbojet technology also receives a lot of R&D money, so they’re constantly introducing improved models that are lighter, cheaper to operate, and cleaner than ever before. And doing so in smaller sizes, so they can go on ever smaller aircraft. Have you seen the jet-powered Sonex homebuilt? It’s a tiny single seat experimental, and even that airplane has been fitted with a jet engine.

      In some ways, that makes the remaining Merlins and their ilk even more special. I hope the advent of 3D printing will allow new parts to be manufactured more easily for these important power plants. After all, they stopped making parts for them half a century ago. Sooner or later it’s going to get very difficult to keep them running, even by today’s warbird standards.

  2. Ray L Rivera
    April 20, 2017 at 8:50 am

    Have you heard of this museum in Indianapolis? The Rolls-Royce Heritage Trust Allison Branch Museum?

    https://www.aopa.org/news-and-media/all-news/2014/may/21/museum-offers-inside-look-at-rolls-royce-allison-engines

    • April 20, 2017 at 10:28 am

      I had not heard of that one, Ray — thank you for pointing it out. Boy, that would really be the ultimate engine display, wouldn’t it? An early turbojet engine which was actually operating inside the museum. I’ve always preferred aviation museums where the airplanes still flew rather than being grounded relics covered in dust. No reason the same shouldn’t go for the engines. As much as he loved the recording of the Merlin, my son would really have been amazed by watching one start up in real life.

      If you ever get out to the museum at March Air Force Base here in Southern California (http://www.marchfield.org/), they have an extensive display of jet engines. Many of them are outside, as I recall, lining the walkway to the pavilion, so they’re not in the best of shape, but it’s a fascinating collection nonetheless. One of the most interesting is a Merlin engine inside a glass display case. It was flown at Reno and the engine case blew apart while running at some obscenely high manifold pressure (150+ inches?). Fascinating stuff.

      • April 20, 2017 at 3:35 pm

        Absolutely! A static engine is way more disappointing than a static aircraft.
        A word of warning though – cover his ears. My son cried the first time I took him to a live engine run… but he did watch the videos over and over and over when we got home.

      • Ray L Rivera
        April 21, 2017 at 5:22 am

        I haven’t been to it yet – but the Allison Branch of the RR Heritage Trust Museum in Indy is all indoors and all the engines and exibits are well taken care of. You’ll be able to see pictures of it if you go to the Museum’s website. There’s something for everyone – children, engineers and non-engineers or folks w/o any technical training. I’ve been communicating with Mr. D.B. Newill (who runs the museum) to arrange a visit. Unfortunately it’s only open weekdays from 10A – 3pm. Here’s his info if you want to contact him:

        D. B. Newill
        President
        Rolls-Royce Heritage Trust, Allison,Branch, Inc
        Street – 7715 North Perimeter Rd. [C/O RCTC]
        Mail – P.O. Box 420 0-14
        Indianapolis, IN 46241
        USA (317) 230-6516 Office
        USA (317) 590-7752 Cell
        HeritageIndy@rolls-royce.com

  3. April 20, 2017 at 3:28 pm

    Coo-ool!! What wouldn’t the airlines and freight haulers give for an engine they only had to shut down once every six years? The Avon was/is a truly remarkable turbine; an absolute expression of Sir Henry Royce’s maxim that “only perfection is good enough”. Given that design work started in 1945, it’s also proof of just how rapidly RR advanced jet technology in that first decade.
    The company has named almost all their production turbines after British rivers, although they have chosen a few that are little more than significant mill streams. Some other products, like the Pegasus (Hawker Harrier) and Olympus (Avro Vulcan, BAC Concorde) inherited names from the original manufacturers.
    This followed a similar convention of naming RR piston engines after birds of prey (not mythical wizards!), right back to the Eagle of 1915. You could argue that the 1918 Condor and the 1928 Buzzard bent this rule; and things got a little more complex during the war: First there was a proposed line of two-stroke engines named after historic battles, which only produced the Crécy (a phenomenal piece of engineering by the way); and then some massive 24-cylinder X-format motors which, built for commercial use, would be named after mountains. The Pennine and Snowdon were both built, but the prototype X was named after, wait for it, a river – the Exe. (Yeah, try and find that one on a map.)
    Anyway, I know it’s accepted that the Merlin is the greatest sounding aero engine ever built and it certainly has a glorious song from idle right through to high-speed fly-past, but the South Australian Aviation Museum (my ‘local’) also has the Merlin’s direct antecedent, a running RR Goshawk from around 1930. It’s a V-12 as well, and was used to power all those gorgeous silver Hawker biplanes of the era.
    Maybe its peacetime watchmakers were under less pressure, or maybe it’s the slightly smaller displacement (1296 cu in to the Merlin’s 1650 cu in) but to my ear it’s possibly even sweeter than its big sibling. It sounds like a tiger! Check one out if you can.

    • April 22, 2017 at 10:04 pm

      I’m just starting to realize how silly it was for me to write this post without talking to you about it first. You undoubtedly have more RR knowledge than just about anyone in my Rolodex! 🙂

      • April 28, 2017 at 4:57 pm

        Oh, I’m just a beginner… But thank you!

  4. April 20, 2017 at 4:18 pm

    Ron,
    Wow, like father like son! Sounds like you (at least) have a budding aviation mechanic on your hands!

    You mentioned the PT-6A, which I think may be the most successful engine in history. When it’s not powering a turboprop, it’s probably powering a jetliner sitting at the gate with the APU (the PT-6) running!

    While I have an engineering degree, the passion for engines never quite took. But, like most pilots, my heart skips a beat to hear a plane like a Spitfire go rocketing by, and I nearly pee my pants at the sound of a P-51!

    Fun post!

    Eric
    capnaux.com

    • April 22, 2017 at 10:08 pm

      I never considered the mechanic/engineering angle, but now that I think about it he does love figuring out how things work.

      I think pilots and mechanics are a lot like homebuilders and pilots: you’re predominantly one or the other, never both in equal measure. I’ve seen pilot-builders who try to build an aircraft, and they typically end up selling a half-completed project. Likewise, the builder-pilots will complete an airplane, and once the first flight is accomplished, they lose interest in their creation.

      People. I’ll never understand them. 🙂

  5. April 20, 2017 at 11:27 pm

    A great read I think all of us avgeeks are RR Merlin fans that noise for start just makes me shiver just the thought of it

    • April 22, 2017 at 9:57 pm

      I think that’s safe to say! If there’s someone out there who doesn’t like the sound of a Merlin, I’ve never met or heard of them. 🙂

  6. April 23, 2017 at 4:52 pm

    I have drifted away from aviation after 14 tears of retirement (mandated by our FAA). I no longer host book events (The Rogue Aviator) but I still enjoy your brilliant blog. As a result of 2 years at the helm of the G-159 I also came to appreciate the reliability of the Rolls- Royce engines. Keep on writing and “keep your airspeed up in the turns.” Allen Morris/aka Ace Abbott

    • April 23, 2017 at 6:23 pm

      Thanks Ace! I’m sad to hear you’re not actively involved anymore; you have so much knowledge and experience to share with the rest of us. The G-159 is a good example of that. It’s such a fascinating aircraft, and a bridge between not just the turboprop and jet worlds, but also the Grumman and Gulfstream eras. Anyway, the Rolls line has brought many pilots back safe and sound, time after time. What better testament to those who designed, built, and maintained them?

  7. June 27, 2017 at 4:07 am

    Wonderful conquer! ! very informative Article Ron .. Thanks for sharing..

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