cool post in silver.....

That is a function of weight, altitude, CG and atmospheric conditions. The airspeed indicator and mach meter display VMO/MMO as the operational certificated limit which changes with the aforementioned parameters and is computed by the air data computers. I have seen mach .89 in a 747. For its size it is a very fast airplane much faster in cruise than the DC-10 and MD-11 partly due to the angle of incidence differences.

I can assure the DC-8, DC-10 and MD-11 all went mach 1 in their respective flight test programs. I dont know anything about Boeing flight test certification?

I have a video of the MD-11 PFD indicating .999 during the certification test of mach 1. This was done out of the Yuma facility. If your interested i will try to find it when i return?

Cheers

 

The larger the airplane the better it works regarding airflow. The 747 is a fast airplane and is supposed to be the fastest commercial airliner today. In the 90's on a flight to Seattle we took off from London one hour late in a 747 SP. The pilot assured us that we would land on time, stating." This airplane can do it." It did.I have been told that it was a .91-.92 airplane.
Switches

 

I have read about the supersonic DC-8 flight that was made out at Edwards AFB it surprises me to read that similar tests were done with other planes. Figured it was kind of like the 707 roll one time event

 

I can assure you the DC-10 and MD-11 went supersonic in their flight tests. My Father was part of the crew in the MD-11. It was ship 449 and he named it the "The Spirit of Hartford"as it was powered by Pratt & Whitney engines. He spent 26 years in Flight Test for McDonell Douglas and was on several projects including the DC-8, DC-10, MD-11, KC-10, MD-90 and several others with other manufacturers including Lockheed.

Here is a pic of this airplane. He is the guy in the middle with the blue hat. He is well known in the aviation flight test community. What flight test experience do you bring to this discussion?

What exactly are your qualifications in the aviation community?

I myself have advanced degrees in aeronautics and have numerous type ratings and have flown over 100 types of aircraft. Please tell us what you have flown to base your conjecture?

The second picture is certification day of the MD-11. The guy in the blue hat is my Father and he is holding the AFM that he mostly wrote. I have seen the video, it went mach 1 believe it or not?
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What is the Mmo in the MD-11?

Generally, airplanes with an Mmo up above 0.85 or so can do it aerodynamically, but there are some issues with the engines in the high transonic regime (or so I've heard). Inlet design, I believe, is key.

 

Good grief, he said he "was surprised", not that it didn't happen. Unless I'm not reading it correctly - I don't have an advanced degree in aeronuatics, or even a type rating in one aircraft.

 

He accuses me of making up stories in another thread. I got the message loud and clear hence the flavor of my response.

Cheers

 

Nah, just thought you were placing a bit too much faith in some people making some rather remarkable claims.

Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?
Douglas Adams

Nothing worth mentioning....... I hear it takes quite a bit to fly those aeroplanes

A guy on the internet saw a video of it? Good enough proof for me!

 

The transonic region from about mach .92 to 1.05 is the worst on most aircraft because the air data (pitot) systems are not usually reliable in that airspeed regime and that can affect the engines as well. Once through that region, things smooth out and the air data systems work quite well. Quite a few aircraft will bump up against the transonic region and not have enough thrust to push through it, especially aircraft that have not been area ruled and do not have supersonic airfoils. Penetration is important for going over mach 1, and even mach 2.5 fighters penetrate the mach easier if the angle of attack is reduced to near 0 at penetration.

A shallow dive is usually sufficient to get an aircraft that can reach transonic velocity through the mach, as long as the intakes work well enough so the fans are not operating in supersonic airflow and want to stall.

There is no reason why a lightly loaded airliner could not make it through the mach as part of a test program as long as the altitude is high enough for q (airloads) not to be problem.

Taz
Terry Phillips

 

Thank you for your precise knowledge in this subject. Those who have experienced the phenomenon of supersonic flight and can accurately define the physics of it are few. I recall the discussions about the inlet lip design of the 707 vs. the DC-8 and their respective attributes. The DC-8 was rounded and operated best on the ground at low airframe speeds. The 707 was sharp and suited for high speed but could suffer from lip stall on the ground with a slight cross flow. Yet the DC-8 still worked well at speeds approaching and beyond Mach 1.. Transonic flow doesn't know what the heck it wants to do and piles up so thick that it takes thrust cubed to get through it. There are many stories about airplanes that get happy once they are beyond Mach 1 and the shock pile up is behind them. You touched on Q (dynamic pressure) reminded me of the Q bellows on the 707 that took readings from the Q mast on the lower fin. That fed " feel" into the powered control system to prevent over-control and destruction at high speed.But you know all about that, I think.
Switches

 

Bob- It helps to have been supersonic well over 100 times. Plus an F-111 would easily cruise at mach 0.92, but altitude hold would not work well, so you had to hand fly it and that could get old after a couple of hours. Mach 0.90 worked fine, and that was the limit for cross country pods and some of the practice weapons dispensers. We even had an F-111F at the 431TES at McClellan AFB (closed) that would supercruise at mach 1.05-1.10, 70-2400. Fastest F-111 any of us ever flew. Got a few noise complants flying down the Sacramento Valley with it.

To get through the mach, we would actually sweep the wings forward to 45 degrees to get the nose down and AOA close to zero to aid penetration. Once through the mach, wings back to 72 degrees. You had to be careful flying the aircraft in turns at 72 degrees WS because the two sets of spoilers locked out progressively at 45-47 degrees of wing sweep, and roll characteristics were different with only differential slab.

Mach 1.2 at 100' is a real blast, but only a few of us got to do it, and it tended to tear up the aircraft because of q loads.

Taz
Terry Phillips

 

Man! That sounds like fun. I remember seeing black and white photos of the standing shock wave on the 707 inboard wing...not condensation but a thick stack of air.