Was Chuck Yeager the First to Break the Sound Barrier?

We all know that Chuck Yeager broke the sound barrier in 1947, but did others beat him to it?

Filed under General Science, Urban Legends

Skeptoid #154
May 19, 2009
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Chuck Yeager and the Bell X-1
Chuck Yeager and the Bell X-1
with paper tape of the
supersonic flight profile
(Photo credit: NASA)

We all know the story of how Captain Chuck Yeager opened the throttles of the Bell X-1 Glamorous Glennis in October, 1947. Breaking the sound barrier was to aviation what Neil Armstrong's first step was to the space program: No matter how many others went higher or faster later, it will always be that seminal, unassailable "first" that can never be topped. Yeager's name will always sit atop every list of record-breaking pilots, up there by himself in his own special stratosphere. But: Was he really the first pilot to fly faster than sound?

Plenty of stories out there say Yeager wasn't the first. How do we know what to believe? Do we accept the popular official story, or do we give credibility to the other claimants with good evidence of their own? Today we're going to point our skeptical eye at some of these other claims, and see who really deserves the credit.

There are certainly many pilots who approached the sound barrier but didn't live to tell about it. The years preceding Yeager's flight were among the most exciting in aviation history, as World War II drove aeronautic advancement like never before. Planes that had been shot down often entered the transonic realm as they plummeted, and were torn apart by the resulting shockwaves. Dive bombers had to have special air brakes developed to prevent them from breaking up, which sometimes happened anyway. Of the many pilots who toyed with the sound barrier in WWII — all unintentionally, of course — most never survived the adventure.

During WWII, engineers didn't yet have any flight test experience that taught us how to design aircraft capable of supersonic speed. Even in 1947, Yeager's X-1 was designed after a 50 caliber bullet, known to be stable at supersonic speeds. WWII had seen widespread use of the German V-2 rockets, which were supersonic, so we knew such flight was possible. But the V-2 was ballistic, it didn't require a controllable airframe; and designing a supersonic controllable airframe was the problem for aeronautical engineers. The main issue is called shock stall, and it's what happens when a control surface approaches the speed of sound. A shockwave forms around the control surface, rendering it useless, and the pilot has no way to control the aircraft.

Propeller aircraft can never reach the sound barrier, since the tips of propeller blades hit the sound barrier before the rest of the plane does. The propeller blades go into shock stall, and the plane can no longer accelerate. There are many claims of propeller driven dive bombers breaking the sound barrier during WWII, but these have to all be considered implausible. Approaching the sound barrier, an airplane is already well above its terminal velocity, the speed at which drag matches the acceleration imparted by gravity. Propellers are shock stalled, and there is neither thrust nor gravity available to accelerate a diving airplane past a certain point. As any aircraft approaches the speed of sound, airflow over some parts of the plane will exceed Mach 1 and create shockwaves. These shockwaves cause intense buffeting. Many propeller driven WWII fighter planes, including the Supermarine Spitfire, the Lockheed P-38 Lightning, and the North American P-51 Mustang, experienced these effects at Mach 0.85. Similarly, jet engines of the day were not designed to work with supersonic airflow entering through the compressor vanes; such engines would flame out.

However, one particular fighter plane of WWII was not driven by either propellers or jets: The German rocket powered Messerschmitt 163 Komet. The Komet was designed by the great Alexander Lippisch, a pioneer of delta wings and ramjets. By the end of WWII, Lippisch had a test glider of a supersonic ramjet powered aircraft actually undergoing flight tests. He understood the requirements of supersonic flight. The Komet was designed to fly as fast as possible while staying under the critical limits at which trouble happens. The Komet's delta wing was exceptionally thin. This delays the onset of shock stall over the primary airfoil, and allowed the Komet to remain stable up to Mach .85. However, Lippisch had no answer for shock stall at the control surfaces on the trailing edge of the delta wing, and so the Komet was destined to remain subsonic. In combination with the relatively low 3,800-lb thrust of the Komet's Walter rocket engine (about half the power of Yeager's X-1), the Komet had little expectation of going supersonic, except in an uncontrollable, powered dive which would probably be unrecoverable.

Nevertheless, stories persist of Komet pilots breaking the sound barrier, years before Yeager did. Komet test pilot Heini Dittmar, flying an early prototype in 1941, reached an officially measured speed of 1,004 kph in level flight. This was probably around Mach .95 but we don't know for sure since the flight was classified until after the war and the altitude is unknown. However, Dittmar made the flight at partial throttle to avoid buffeting, using an engine only half as powerful as that which went into production. But just because later versions were more powerful doesn't mean they wouldn't run into exactly the same limitations at the same top speed. One unofficial report claims that Dittmar hit 1,130 kph in 1944 (Mach 1.06), and another states that in a steep dive he created sonic booms that were heard on the ground. However, these stories first appeared in 1990 book written by Dittmar's friend Mano Ziegler, and do not have contemporary corroboration or documentation. But the best evidence against Komets breaking the sound barrier is the fact that the Allies did capture all of the program's classified data, and no supersonic flights were ever recorded, even in secret.

Claims you'll find on the Internet that "Komet pilots routinely broke the sound barrier" cannot be given much weight, given the aircraft's limitations well understood by Alexander Lippisch. As an aircraft approaches the speed of sound, the shockwave over the wing moves the center of lift backwards and the plane noses down. This is a condition called Mach tuck. Normally you'd pull back on the stick to correct this, but conventional elevator controls on the trailing edge of the tailplane would be unable to get any bite, since the elevators would be shock stalled. The only way out of Mach tuck is to use an all-moving tailplane to trim back to level. With its delta wing, the Komet had no tailplane at all, let alone an all-moving tailplane. It had fabric-covered elevons on the trailing edge of the delta wing, which would always be shock stalled. Even if a pilot opened his Komet's rocket engine to full throttle to muscle his way past the sound barrier, Mach tuck would send him tumbling out of control irrecoverably, and probably destroy the airframe.

It's also important to be aware of a limitation of early airspeed indicators. One built for subsonic speed is probably going to give unreliable readings in the presence of shockwaves. A phenomenon called compressibility error gives inaccurately high airspeed readings as the aircraft approaches the speed of sound. This error is called Mach jump. To counter this, supersonic aircraft use a Mach indicator instead of an airspeed indicator. The speed of sound at any given pressure and altitude is determined primarily by temperature. A Mach indicator is essentially an airspeed indicator mounted on an aneroid diaphragm to correct for static air pressure. Since Mach and airspeed are both dependent on temperature, they cancel each other out and no temperature diaphragm is needed. Komets had airspeed indicators, not Mach indicators; and so even the speeds logged by the German test pilots are probably incorrectly high.

One of the best known claims to the sound barrier comes from German WWII fighter pilot Hans Guido Mutke, flying perhaps the most devastating fighter of the war, the Messerschmitt Me-262. The 262 was the first true operational jet powered fighter plane in the world, sporting twin BMW 003 turbojet engines mounted below the swept wings. Although the 262 entered the war too late to have any real impact, it boasted a 5:1 kill ratio against allied fighters. Mutke was cruising at 36,000 feet when he began a steep dive under full power. With his airspeed indicator pegged at its limit of 1,100 kph (just over the speed of sound, but remember the airspeed indicator problem), Mutke reported severe buffeting and loss of control. Suddenly the buffeting stopped and he regained control, with the airspeed indicator still pegged; and it's this that could indicate he had broken the sound barrier. Unfortunately his engines flamed out, not being designed for supersonic speeds, and he slowed, and the severe buffeting returned. Finally his speed dropped enough that he regained control again and was able to restart his engines. He returned to base, and it was found that his aircraft had lost many rivets, and its wings had become so distorted that the plane had to be scrapped.

Mutke never understood what had happened until Chuck Yeager's flight was declassified and the supersonic flight profile became known: Severe buffeting while approaching Mach 1, then the shaking stops above Mach 1, and then resumes upon deceleration below Mach 1. But unfortunately for Mutke, there was not, and could not have been, any independent verification of his speed or of the period of smooth supersonic flight. Nobody denies the damage done to his plane during the buffeting period, but supersonic flight was not necessary for this to happen.

The designer of the Me-262, Willy Messerschmitt, always stated emphatically that the 262 was incapable of supersonic flight. In flight tests, he found that at Mach 0.86, the 262 experienced Mach tuck: It lost control and assumed a nose-down attitude that could not be corrected by the pilot, and throttling down was the only way to resume control. The 262 only had conventional elevators on the trailing edge of its tailplane, like all aircraft of the day, so these would have shock stalled and not been able to correct the Mach tuck. But the 262 also had an additional feature: The tailplane was actually all-moving for trim purposes. This was a separate electrically operated control, and it was normally used to keep the plane level as its fuel supply was consumed. Mutke reported that he actually employed this all-moving trim control in order to get out of the nose-down state, a technique which may not have been considered in Messerschmitt's own tests. Mutke's report was given additional credibility in 1999, when computer modeling and scale model wind tunnel testing conducted at Munich Technical University found that the 262 was capable of reaching, and passing, Mach 1.

$2/mo $5/mo $10/mo One time

So, while we cannot prove or disprove Mutke's claim, it is possible that he did reach supersonic flight. However, like in sports, it's not what happened, it's what the referee says happened that matters. Mutke's feat was unverified and unofficial, and certainly unintentional; so even if he did break the sound barrier before Yeager, it "doesn't count."

There are two other flights that don't count, both accomplished by George Welch, a civilian test pilot for North American Aviation. On October 1, 1947, just 13 days before Yeager broke the sound barrier in the X-1, Welch took the new XP-86 fighter prototype up for its maiden flight. In a powered dive from 35,000 feet, Welch reported Mach jump on his airspeed indicator, showing that he was traveling supersonic. Anecdotal stories say that a sonic boom was heard on the ground. Welch's airspeed was not being officially recorded, and no official record states that he broke the sound barrier. If he did, it was either unverified or classified. Welch believed that he did, and to hammer the point home, he gave a repeat performance. While Yeager was strapped into the X-1 still attached to its B-50 mother ship, just before the historic flight, Welch again put his XP-86 into a steep dive. Some stories say that he buzzed the B-50 close enough for those onboard, Yeager included, to hear his sonic boom. He made a 4g pullout from his dive, and those same stories say that his sonic boom was louder than Yeager's just 20 minutes later.

There is no engineering reason to doubt Welch's claim. The history books credit George Welch with breaking the sound barrier in the XP-86 in a dive six months later on April 26, 1948, with official measurements and a proper Mach indicator on board. Did he do the same thing before Yeager's flight? He may well have, and a lot of people say he did. But there's a significant difference between Yeager's flight and those of Welch, Mutke, Dittmar, and probably others. Their claims to the sound barrier were all in dives, and were transient at best. Glamorous Glennis, on the other hand, was the first aircraft capable of sustained supersonic level flight. Sure, being the first to break the sound barrier becomes less glitzy when you have to pile on qualifications. But every aviation milestone has been an incremental one; few are truly revolutionary. Yeager, Welch, Mutke, and Dittmar all made real contributions to the science of aviation. All had "the right stuff". At some point, any lines you draw to separate their achievements come down to semantics; yet you still have to draw those lines somewhere. Flights have to be official, they have to be verifiable, and they should demonstrate a deliberate capability. And so, while it's a virtual certainty that the sound barrier was broken by someone somewhere in some circumstance, Chuck Yeager's flight of the Bell X-1 is the only flight to meet all the criteria of a true aviation first.

Follow me on Twitter @BrianDunning.

Brian Dunning

© 2009 Skeptoid Media, Inc. Copyright information

References & Further Reading

Hilton, William F. High-Speed Aerodynamics. London: Longmans, Green and Co., 1952. 15-19, and Ch. 6.

L.J. Clancey. Aerodynamics. Ney York: Wiley, John & Sons, Incorporated, 1975. 283, 415.

Mason, W.H. Configuration Aerodynamics. Blacksburg, VA: Virginia Tech, 2006. Chapter 7.

Rotundo, Louis C. Into the Unknown: The X-1 Story. Washingon, D.C.: Smithsonian Institute Press, 1994.

Wagner, Ray. The North American Sabre. London: Macdonald, 1963.

Yeager, Chuck, et. al. The Quest for Mach One: A First Person Account of Breaking the Sound Barrier. New York: Penguin Studio, 1997.

Reference this article:
Dunning, B. "Was Chuck Yeager the First to Break the Sound Barrier?" Skeptoid Podcast. Skeptoid Media, Inc., 19 May 2009. Web. 19 Apr 2014. <http://skeptoid.com/episodes/4154>

Discuss!

10 most recent comments | Show all 46 comments

Red Adair signed my Ginger Rogers prize fan photo..

Yep, in the days when risk was astounding there were guys who just kept punching way above their weight.

You'd wonder nowadays what it took to get a guy to be an astronaut in the 60's.

Its still a very risky business!

Moral Dolphin, Greenacres by the sea Oz
May 28, 2013 2:47am

Perhaps 3-4 years ago I contacted the USAF historical office and asked whether Yeager or Welch was "the first." Their answer was ... "Welch was probasbly the first in his F-86, but certainly he did it in a dive, and we only recognize records set in level flight. Thus our definition is that Yeager was the first in level flight." So the USAF historical office believes that Welch really was the first. Accordinly, the placque in the Hartford Air Museum credits Yeager as being the first in level flight.

harry schmidt, cromwell ct
July 13, 2013 6:14pm

I just found this podcast and find it very informative.

It also clearly shows how "firsts" are more shaped by political, national, and agenda issues than fact.

We have seen this in such things as who was the first to find america, who was the first black female to refuse to give up her seat (it was not rosa parks) or first to invent the radio (to name a few).

Some not only took years to correct, but still are still being published even in the face of fact.

If you want an example just look up the court case of tesla and edison over the radio (BTW it was tesla per the courts).

The thing that sticks in my craw is this moving of the goalposts in supersonic flight.

First the prop dive bombers were doing it, but not allowed due to "supposedly" no one survived the "inevitable breakup" of aircraft.

Then the nazi did it with jets but "not verified" by allies (but reports showed they did).

All before also discredited due to "no mach guages" but reports all showed the buffeting and booms.

Then a pilot did it TWICE before yagers flight.

In the final crack they stated well yes he did but not in LEVEL FLIGHT.

Funny no where untill that did level flight become a requirement.

If you want to say yegar was first in LEVEL FLIGHT maybe.

But in no way was he the first "to live to tell the tale".

I guess (in this case) i have to ask WHY was it so important that only yegar got the credit?

Eric, Northern IL USA
July 28, 2013 1:06am

If its dive sound barrier, wouldnt the brit tempest based series be the first and regular?

Now there was a prop speed machine?

I have no doubt that the fascist rocket and jet birds may have broken a lot of records..I wouldnt recognise any positives from that regime.

Madime Dantefer, Greenacres by the sea Oz
August 14, 2013 5:18am

Madime

I am not in any way supporting the Facist or Nazi regime.

But we need to recognize who was first for if no other reason than for the reason of HONESTY.

Just for example should we discount sputnik just because the government who sent it up was an evil communistic nation?

No they were the first and has been recognized as such.

I just showing (in the sound barrier) just one of many "firsts" that in reality not only were not, but recognized as such due to political/national/agenda oriented reasons.

But also in the case of the radio the history reporters STILL report someone else when the courts CLEARLY showed it was tesla.

Sad to think how many more such "firsts" are left inaccurate/false.

Eric, Northern IL USA
August 15, 2013 1:01am

Sorry If I am a tad late on this one,

Brian was pretty fair and even handed in his podcast and he deals with claim and verifiability for breaking the sound barrier in flight including the US claims and the german claims.

These are mentioned in your above earlier but the verifiability is the key factor here. The instruments and record.

Brian does admit that other may have good claim for the record in craft that weren't equipped to make or record the attempts/events but essentially were dismissed for exactly the same reason. The award thus going to the Bell craft (fairly or not, hardly revisitable .. verifiablilty establishment).

I apologise for the senior moment of Aug 15, but will reiterate that the Nazis made many claims and did indeed produce many firsts and in this case, being no instrumental verifiability, I would not award those claims other than being claims (I think you have a minor state to state kerfuffle over an unverified claim vs the Wright brothers at this moment).

On USSR (or CCCP) and the Sputnik, this was verified internationally from memory.

On pedantry, if you are referring to a utopian workers state as being communist against a recognised socialist/communist union overseen totalitarian central committee being "communistic" your term may be correct. I think they would refer to themselves as communists.

Note my often made distinction wrt "conspiracists" (i.e Theory? Ha!).

Tesla (successes, claims and mythology) is a completely different matter.

Matinee Digress, Greenacres by the sea Oz
August 19, 2013 4:07am

Matinee I must diagree with your idea that germany did not verify that they broke the sound barrier.

I would propose that just one verification (in this case a mach gauge) is not the only way to verify it.

First in the article stated that the early gauges were not "accurate".

However when they were combined with the now KNOWN effects of breaking the sound barrier such as the buffetting, control problems and that pesky verifiable sonic boom then taken as a whole YES IT IS PROOF.

IN the nazi germany case they were fanatical record keepers when it came to technology. The records of the breaking the sonic barrier are there as well as the records of USA testing the same (ex) aircraft thus verifying it.

Now what I consider proof of my assertion of "firsts" being more political is what was clearly stated by brian in relation to chuck yager. The other pilot mentioned not only broke the sound barrier TWICE before yager flight.

But the air force clearly ADDED THE CAVIAT of LEVEL FLIGHT.

Now how can you say on one hand there is no verifiable proof but then defend the premise ADDED AFTER THE FACT that it had to be level flight.

As for the other examples (rosa parks and tesla) space limits a good response but suffice to say the proof (in tesla being the SUPREME COURT) is clearly there.

Unpopular perhaps but there

Eric, Northern IL USA
September 04, 2013 4:20am

1) A claim that isnt verified isn't a record.
2) a post hoc claim on a claim is not a verification of that claim and hence not a record.

Both are missed opportunities at best.

3) question begging is not an argument.

4) A court case isn't much of a place to sort out any sort of measurement (Please note Kent Hovind's position on court cases has radically changed). It is a great place to settle complicated disputes (Please note the IRS and Kent Hovind's current position).

You can challenge a record with some verifiability. You can challenge a verdict with a whole raft of challenges.

Manki Drain, Big IL, USO
October 03, 2013 5:48pm

Sorry manki but you are trying do deny something just due to the fact it either was not recorded and or verified because it was by someone/group that YOU DO NOT HOLD IN HIGH REGARD.

First on the German Nazi claim. They kept EXTENSIVE RECORDS that were the basis and GUIDLINE that ADVANCED our aviation program by DECADES. In those records they CLEARLY SHOWED the same evidence of supersonic flight that was REPEATED by our own scientists. It is because they were NAZI's that the issue of who first is decided.

Ironically note that the same scientists who logged the claims you so dismiss WERE THE SAME ONES WHO WORKED ON THE APPROVED programs you claim are the first.

Isnt it hypocritical to claim when SAME SCIENTIST broke the sound barrier for Germany its a "claim" but for America its fact.

Second the very pilot who broke the sound barrier TWICE but discredited due to "being in a dive" had the magic "mach guage" and all the credentials that yager had.
But he was not told till AFTER that it had to be in level flight.

Lastly as to the crack about the courts. Last I checked they have an impartial judge who DEMANDS evidence from the parties in disagreement then judges which is more credible.

Hmmm isn't that what science is supposed to be about?

In conclusion Manki it does not matter who did the first political/social/status is FIRST IS FIRST.

Otherwise why give the communist (bad guys by ANY STANDARD) the first in space travel?

Eric, Northern IL USA
November 06, 2013 12:13pm

A couple quick nitpicks on the Me-262. First, its wings were BARELY swept - 18.5 degrees, not enough to do much good near mach 1. Second, although the BMW 003 was in the original design and a few of the prototypes, that engine wasn't ready by the time the plane finally went into production, so the airframe was slightly redesigned to accept the Junkers Jumo 004 engine, which is what all production models utilized.

Jason, Cincinnati
April 08, 2014 9:15am

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