The Business Jet Speed Race

More than 15 years ago the Cessna Citation X pushed through the Mach .90 barrier to become the fastest civilian airplane with an Mmo (maximum Mach operating speed) of Mach .92. At the altitude where business jets typically cruise above 36,000 feet Mach .92 equals about 528 knots true airspeed.

When Gulfstream developed the G650, the largest cabin and longest range business jet, and the fastest, it upped the ante giving the airplane an Mmo of Mach .925. That put the maximum operating speed of the G650 about 3 knots faster than the Citation X.

Cessna is developing a new, stretched version of the X and changed the name to the Ten. The X is the Roman numeral for 10, but not everyone made that connection, so this time Cessna is spelling it out. The Ten has a longer cabin, and new touch screen flat glass avionics from Garmin, and more efficient versions of the Rolls-Royce engines. And it has winglets.

Most of us expected Cessna to try to find a way to eek out a little more speed to reclaim the fastest business jet title, and the company recently announced that it plans to certify to an Mmo of Mach .935, which is .01 Mach faster than the G650.

Obviously, this is a game of bragging rights because .01 Mach is less than 6 knots of true airspeed which will be hard to find even on a long trip. But still, bragging rights are important. And both companies are bumping up against the unyielding sound barrier at Mach 1.0.

Mmo is a certification requirement for jets and is the indicated Mach operating limit. Jets have two red line airspeeds—Mmo, and Vmo. The Vmo is an indicated airspeed limit and is set primarily by the structural loads on the airplane. Indicated airspeed is a measure of air pressure the airplane experiences and that air pressure stresses the airframe so there must be a maximum indicated airspeed.

However, at higher altitudes where air density is low, indicated airspeed is also low, but the effects of Mach—compressibility—become the limiting factor. Even though an airplane is flying well below Mach 1, the speed of sound, the air accelerating to pass over the wings, tail and fuselage does reach Mach 1, or faster. At Mach 1, or actually a little slower, a shock wave develops which creates high drag, but can also affect flying qualities.

The Mach shock wave initially forms near the leading edges of the wings and tail, or over the canopy of the fuselage, and then the wave moves aft as the airplane accelerates. The lifting characteristics of the wing and tail change with movement of the shock wave so flying qualities and stability can also change. When an airplane flies fast enough the Mach shock wave can move aft over the flight control hinge lines, or onto the flight control surfaces and that can cause very serious control problems in an airplane not designed for that speed.

To give pilots a safety margin the FAA requires new jets be tested to a speed called Md, which stands for maximum Mach demonstrated dive speed. Md must be faster than Mmo so that if the airplane is momentarily upset and noses down and accelerates past Mmo, the pilots know that nothing bad will happens while they regain control of the speed. In general, Md must be .07 Mach higher than the design Mmo. There are some analytical ways to get the difference between Md and Mmo down to .05 Mach—including the use of automatic devices to slow the airplane—but Md will need to be at least .05 Mach above the certified Mmo.

But Mach 1 is there as a cap on Md speed. It requires special permission and procedures for a civilian airplane to exceed Mach 1, and it’s unclear that the FAA would approve a Mach dive test faster than the speed of sound. Both Cessna and Gulfstream dance around the question of how fast their jets went during dive tests, but even as good as their test pilots are, it’s impossible to believe either airplane was able to dive to the required Mach .99 and then slow before hitting Mach 1. But that’s their story and they are sticking to it.

So with Cessna aiming to certify an Mmo of Mach .935 there is not much room left for the dive test and a faster Mmo. Can Gulfstream squeeze in with an Mmo of Mach .94. It will be tough under the rules, but they could probably match Cessna’s Mach .935.

Which airplane is fastest? Well, the G650 has a provisional certificate and first deliveries will be made later this year so its Mmo of Mach .925 is already in the bank. Cessna is confident it can certify to its announced speed, but that is yet to come.

As for which has the real world usable speed advantage that goes to the G650 hands down. Gulfstream test pilots flew a G650 for 5,000 nm at a constant speed of Mach .90. No other jet has flown that fast that far except for a few dashes by military airplanes that refueled in flight. The Citation Ten expected maximum range is 3,242 nm and that comes at a leisurely Mach .82 cruise speed so you can see which airplane will get you a long way the quickest.

But there are those bragging rights and we can all enjoy watching Cessna and Gulfstream look for hundredths of a Mach while knocking on the Mach 1 door.

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30 Responses to The Business Jet Speed Race

  1. Ramiro Silveira says:

    Hi Mac,

    Just one note, actually Md is de design dive mach, while Mdf is the demonstrated dive mach, basically that one the test pilots obtain after flying for 20 s in a flight path 7.5 deg below the one they had when stabilized at Mmo, then perform a pull up maintaining 1.5 g max with engines in idle, being allowed to use speed brakes.
    Regards,

    Ramiro

    • Mac says:

      Thanks, Ramiro. Sorry to confuse the two test points. I Mach dive I described is the Md, or design speed, not the demonstrated acceleration with the nose down as you note.
      Bests,
      Mac Mc

  2. David Matthews says:

    Hi Mac,
    Am I missing something here?
    When the Citation X bragged about being “the fastest civilian aircraft with an Mmo of M.92″ all those years ago, I said to myself, “No, not true” and waited for someone to object! Seems either no one did, or I missed it IF they did, or I misunderstood the qualifying statement, “civilian aircraft”!
    I believe that a Boeing 747 IS a civilian aircraft, and if that is a true statement, then Cessna’s claim is NOT true. Since it first flew in 1969, the 747 and all the models, the SP, 100,200,300 & 400, ALL have an Mmo of M.92.
    So what am I missing here?
    Thanks
    Regards
    David

    • Mac says:

      You’re right, I believe, about 747-400 and later having Mmo of Mach .92. Earlier versions were Mach .89. The correct way–until the G650 and now the expected Mmo of the Citation Ten, is that the Citation X is the fastest business jet. The 747 has long been one of the fastest civilian airplanes with a normal cruise of Mach .85 when most other jets, including business had normal cruise of Mach .82 or lower. For the G650 Mach .85 is long range cruise, and if you only need to go 5,000 nm or a few more, then Mach .90 is the speed.
      Mac Mc

      • David Matthews says:

        Mac,
        Thanks for the reply.
        I hate to correct you, but I must in order to emphasize the point about the 747 having a certified Mmo of .92 long before the Citation X was even thought of!
        Type Certificate data sheet No. A20WE lists the 747-100 as having airspeed limits of Vmo/Mmo 375/0.92 (KEAS), approved December 30, 1969.
        All the 747 models have the same Mach limit (.92), except for the new 747-8, which is now M0.90.
        David
        PS.. Vmo is 365 for both the -400 and -8.

  3. LeMar says:

    And how does this relate to Experimental Aviation. Or Sport Aviation?

    • Mac says:

      It’s hard to think of anything more experimental than the Mach dive test. It can hold surprises, and not that many years, the Md test of the SJ30 ended in loss of control and a fatal crash. Experimental aviation at the far edge.
      Mac Mc

  4. Steve Pierce says:

    Mac needs to go back to Flying magazine where people care about such things. Go fly a Cub at 300 feet and write about it or rebuild a classic or build an experimental. Get in touch with the readership of SPORT Aviation.

  5. Michael R. Moody says:

    This is one of the reasons I cancelled my membership with EAA.

    • Mac says:

      I suppose you guys hate Neil Armstrong too since he flew fast enough to leave earth’s gravity. Seems to me an EAAer is interested in anything that flies whether it be SpaceShip One or a Pober Pixy. I think business jets knocking on the door of the sound barrier fit somewhere between those aircraft.
      Bests,
      Mac Mc

      • Kelly says:

        Agree with your comment here Mac. While some EAA members are all about building, others are all about aviation, and thinking outside the box. I for one was glad when the Flying troops joined EAA. Keep the articles flowing my friend.
        (FYI – I fly an RV-6A I built, and is the first aircraft I’ve owned)

  6. EAA is about aviation in all its forms – all the way from classics and warbirds to spaceflight – we share, we learn, we apply. Let’s keep an open mind and enjoy this wonderful arena from one extreme to the other!

  7. Gilbert says:

    I think Sport Aviation Mag is trying to be everything for everybody. Doesn’t work for me. I joined the EAA to learn how to build an airplane and then moved on to other forms or recreational aircraft. If I want to read about NASA and space I don’t look for it in Sport Avaition and I don’t expect to read about the latest Business Jet there either.
    Mac needs to get out of the office, fly the VFR approach into AirVenture in an antique traildragger and then visit a bunch of EAA Chapter meetings and find out what a lot of us think the EAA is about.

    It’s not about IFR flights in a Beech twin either.

  8. Robert Smith says:

    Mac,
    Have you been paying attention to the feedback that the membership of “our” organization has been providing you?? It appears from your responses that your views are more important to you that the views of those you serve. As a 30+ year member of EAA, I respectfully submit that you consider that it is the memberships’ desires that matter and that have made it clear that their interests are not to read articles leftover from your Flying archives. Do the honorable thing, jump in the Baron and fly away at Mmo.

  9. Patrick says:

    Ok so those biz jet guys are knocking on the door of Mach 1. Us lowly birds are limited to a measly 250 kts IAS below 10k. I know several exp singles that can bust this easily. What is the history behind this number and as technology improves and speed increases what the likelihood of this number being raised?

  10. SkyGuy says:

    Mac….told you so months ago….you are out of touch with GA.

  11. Fly Guy says:

    Well…I have to say that as an aviator I enjoy all aspects of flight…from the hang gliding to the space station…

    I have no problem with Air and Space Magazine that does a heck of a job covering everything under the big tent of flying…

    However…I think there is a big change going on here at EAA…the new guy in charge has brought in Mac because he wants to run a profitable business…Mac knows on which side his bread is buttered…and the big dough comes from business aviation…just flip through the pages of Flying mag and see who is doing the advertising…bizjet makers…fractionals…big avioinics makers…etc…

    Mr. Hightower apparently thought it would be great to get in on this action and so he put Mac in charge of publications…This means that the editorial content is going to be oriented towards puffing up the business aviation…and at the same time that is why you are seeing more and more glossy advertising from these outfits…

    So whether the EAA membership likes it or not…this is where the EAA publications are heading…a big focus on business aviation

    It’s too bad…because it says making money is job one at EAA…

    And btw…you won’t see any of this gladhanding of buisiness aviation at Air & Space…as part of the Smithsonian they don’t need to…

    But here at EAA we can look forward to more and more articles about $50 million bizjets and super expensive glass panels…

  12. Nick says:

    I’m an EAA member and an engineer. I found this to be an interesting article, like most of Mac’s (sure, “tarmac” may have been a miss, but I don’t bat 1.000 either). If it’s not liked, don’t read the column. There are plenty of others. Thank you.

    • kilo papa says:

      I agree with Nick. Why do these whiny titty-babies continue to read the column of a writer that they apparently have little to nothing in common with.

      I’m sure that the EAA has other writers that will satisfy those who are only interested in reading about experimental aircraft. But if it’s about airplanes, whatever the type, I’m interested.

      • Steve Pierce says:

        Interesting that you can call people names but have to hide behind a handle yourself. My concern is the trend in EAA. Look at Oshkosh and Sun & Fun. So many widget vendors and car dealers. Not near the aviation related vendors that there used to be. Look at how many Vintage airplanes are at Oshkosh, then look at Vintage magazine and the content. Doesn’t appear to me that the resources balance out with the number of airplanes and owners and interested members. It is a concern I have had for quite some time and have discussed with many including some of the decision makers within EAA. I see this as a forum to voice my concerns and not be called names for it.

        • Hal says:

          Steve,
          In principle – agreed. You have valid points, and have stated them clearly and eloquently – this time around. But in your last post you were not. Telling a respectable fellow aeronaut and writer, where he ought to go, and alluding that the rest of us EAAer’s are with you on this, was not in the spirit of aviation or the EAA. I am, and have been a proud member, because we are a unique, caring, and responsible group. We should never allow the rudeness of the outside political arena taint our conduct.

          • Steve Pierce says:

            I guess it is my continuing frustration with what I see as a major change in something I feel so passionate about. I believe there are more EAA members interested in SPORT aviation than IFR flying and business jets by looking at the number of PPL vs. IFR pilots and the number of Experimental and Vintage aircraft at gatherings like OSH. I do not think Mac is in touch with our kind of flying and it is my opinion that the editor of Sport Aviation should be. Jack Cox (former editor of Sport Aviation) was in touch. Really enjoyed his articles and many visits with him and Golda at S&F over the years. He truly loved these little airplanes and the people that owned, flew and restored them.

  13. Hal says:

    Are we missing something here? There are four other ‘interest specific’ magazines put out by the EAA; Experimenter, Light Plane World, Vintage Aircraft Online, and Warbirds Briefing. Why can’t we accept an interesting, intelligent article on pushing the envelope in Sport Aviation? So someone has been a member of EAA for 30 years, and I have been for twenty two years, does that mean I can ‘demand’ this and that? If we were to take votes, my vote goes for intelligent, informative, aviation articles, like this one.

  14. Hal says:

    Steve,
    I must agree with your points on the general drift, away from our grass roots. There is a lot of truth to the ‘commercialization’ aspect tipping the balance away from what matters most. I used to count the months, days, and hours, to the next OSH or S&F, not anymore…
    We may not be able to bring back the old days, but we may still be able to restore the old ways. I am sure folks like Mac can, and do appreciate, the necessity, and urgency, of restoring some of that lost vitality. There has to be a better way forward from here…

  15. Fly Guy says:

    I enjoyed this article…just like I have enjoyed lots of Mac’s articles about bizjets in Flying…

    There is nothing wrong with that…but the point is that EAA is running magazines that get advertising dollars…that is what it is all about…

    There is a fine line between an article that tells us something new and exciting in the world of bizjets…and one that is simply a lot of fluff that no aviator cares about…but is the type of content pushed by business aviation and their legions of PR hacks…

    The fact is that now it looks like more and more we are going to be seeing articles about business aviation that have very little news value or anything else of interest to the little guy aviator…this is what happens when one is trying to please the big bucks advertisers…

    I see that Experimenter newsletter has been totally revamped and is now just a slick little “enthusiast” magazine…I much preferred the old version where a lot of the content was supplied by us…people who are actually building and experimenting…

    But guess what…the deep pocket business aviation community was not interested in advertising in a little grassroots magazine like that…so in comes Mac to turn it into a slick little version of Flying magazine…complete with throwaway fluff articles that do nothing for anyone actually taking part in the homebuilt aircraft hobby…

    Again…this is not a knock against Mac’s articles on bizjets or on radar dishes or on expensive glass panels or on flying IFR 100 percent of the time…there is a place for that kind of content…and it is called Flying Magazine…

  16. Tom Miller says:

    Once again, Mac, I appreciate the variety in your posts.

    I’m a long-time EAA type who loves to fly both VFR AND IFR in my experimental aircraft. I know the low-and-slow folks enjoy what they do, but they’re not the only ones in the sky flying experimentals. Their ongoing insinuation that experimental aviation is only about weed hopping is not appreciated by those of us who use our aircraft both for fun and for practical transportation.

    That said, I do believe the majority of EAA members aren’t in the 1%. The G650 is for the top 1% of the 1%, so I can understand the desire to read about stuff they–and I–actually do in our aircraft or might be able to do in the future.

  17. Chris Gresham says:

    I’ve been reading Mac for longer than I hope to admit, and I like the professionalism and insights he brings to any article, magazine, or blog (at this time in history, anyway). I grew up with the “small” EAA and its devotees to the grass roots of aviation and the like; however, if we are to survive, we – and I do mean EAA, GAMA, NBAA, and all the other alphabet monikers out there – we have to continue to identify and know what’s happening “across borders.” When I read the EAA newsletter, I’m not looking for an article on the G650 or even the Citation X, but the reality of it says that we should at least pay attention to it as it does relate to us in the “lower levels” of aviation. Since we’re all interested in speed (just look around, even at the J3 Cub over the years, among others), this relates to us in a slightly different way, but it is relevant nonetheless. There’s “learnin to be done” at any level, and I for one enjoy differing subjects and variety as “we” grow this new aviation frontier we now face.

    The higher levels of aviation trickle down to us in some way or another, and it should ALL be of interest to us. Now, whether or not you wish or choose to follow it is your own matter, and you will see all sorts of articles in the newsletter that have little to do with the EAA, directly; but I say that it does. The experiementer, whether it be you and me or Bell or Boeing is still the experimenter; and we are pushing the limits of our own arena be it speed and Mach 1 or 100mph.

    You should find it interesting that there are many, many “professional” pilots and astronauts, including Neil Armstrong and others, who are EAA members, and they are for a reason. Now, why can’t it be the other way around so that we include those “from above?” Hoot Gibson has piloted the Space Shuttle into space 5 times, and yet, he’s designed and built his own aircraft for the fun and challenge of it. Why wouldn’t we listen to an article of his as we would for Mac?

    There’s a lot from which to choose in the EAA newsletter and in Sport Aviation, and in most cases, I choose to read all of it. However, I do leave out articles here and there that just don’t interest me for a variety of reasons; or I read the intro on the front page and leave it at that. That’s the nice thing about the newsletter format. It gives you a front page that tells you a little about what’s there, and if you want more, then click and read; if not, just move on.

    So, do I care about a business jet blasting along at Mach .935 knowing I’ll never be in one, much less piloting one? Yep, I certainly do! It’s called aviation, and it IS all about US; from pedal power to rocket power.

    Thank you, Mac. We might not always see eye to eye, but thank you for bringing us the in depth info you do. Your knowledge, experience, and insight into things aviation make you an invaluable part of my continuing aviation “education,” and I’m glad you’ve found a home with the EAA.

  18. Alex Kovnat says:

    That there are business jets flying above Mach 0.9 is noteworthy. I hope a day will come when bizjets flying long-range routes, will do so at Mach 1.5 – 2.0. If supersonic bizjets would help energetic entrepreneurs who create jobs for hundreds or even thousands of people (while bringing us new products like the iPhone) to make more efficient use of their time, I’m all in favor of it.

    But its also newsworthy that we are seeing record speeds for turbine aircraft burning less than 100 gallons of Jet A per hour. For example, the Eclipse jet can hold 400 statute miles per hour while burning ~60 gallons per hour while flying three people from, for example, Detroit to New York.

    We should also note record speeds by aircraft which do not have to charge down a runway at the beginning and end of every flight. For example the Eurocopter X3 (“X cubed”) can fly as fast as a sleek Mooney single engine piston retractable, yet land anywhere a Sikorsky S-76 can. And then there’s the V-22, which flies not quite as fast as a Beechcraft 250 but, unlike the 250, doesn’t a runway to take off and land.

    We have also seen record speeds for general aviation piston planes, such as the aforementioned Mooneys. And, record speeds for single engine piston planes which do not subject their owners to the problems of maintaining (and remembering to lower before landing!) retractable landing gear.

    Given that aircraft like the Eclipse can attain 400 statute miles per hour with less fuel burn than aircraft of lesser speed would have required in the past, one cannot emphasize enough how stupid it is for the government to charge $100/leg for IFR services just because an aircraft is turbine rather than piston powered.

  19. Martin Schroeder says:

    I am all for articles about aviation, whatever the kind. Mac has a long history of writing good, thought-provoking articles. The “haters” who wish to see him leave or move are undoubtedly in the minority, or he would be out of a job.

    As to the influence of business jet and glass panel advertising, I am curious: how many of those who complain about such advertising would support the EAA or Sport Aviation magazine, were they to raise their prices commensurate with the LOSS of those revenue dollars? I suspect many of the same complainers would carp even more about a doubling or tripling of their dues, or would just leave.

    As for me, I’ll continue to support the EAA because I enjoy it, and I’ll read those articles and writers which interest me, and pass over those which don’t!

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