What is 737's Critical Mach no.?
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
Hachiouji-shi,
Until someone comes along with the answer you're looking for, it's a pretty fair estimate that on pre-super critical winged aircraft, Mcrit is approximately equal to your Climb Mach No., or your Long Range Cruise Mach No. minus 0.02 or 0.03
Just 'ball park' figures to keep you going until the exact answer comes along. Given the large number of B737 models and their derivatives, stand by for a lot of different answers.
Regards,
Old Smokey
Until someone comes along with the answer you're looking for, it's a pretty fair estimate that on pre-super critical winged aircraft, Mcrit is approximately equal to your Climb Mach No., or your Long Range Cruise Mach No. minus 0.02 or 0.03
Just 'ball park' figures to keep you going until the exact answer comes along. Given the large number of B737 models and their derivatives, stand by for a lot of different answers.
Regards,
Old Smokey
Thread Starter
Join Date: Nov 2002
Location: Everywhere
Posts: 108
Likes: 0
Received 0 Likes
on
0 Posts
I believe 0.74 is the usual climb Mach or if only .02 to .03 below the LRC, that would mean the 737 operates mostly at it's Mcrit? bit uncomfy ?
and yes, Why did they decide to call that other wing we mentioned, SUPER CRITICAL wing?
and yes, Why did they decide to call that other wing we mentioned, SUPER CRITICAL wing?
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
Hachiouji-shi,
A bit uncomfy operating above Mcrit ? You'd better get used to it, ALL cruise Mach Numbers are above Mcrit, even Maximum Range Cruise, the lowest en-route speed that you'd ever want to fly. Similarly, the Mach Number phase of descent is typically above Mcrit, unless you've opted for the Maximum Range Descent which tends to be somewhat slower. Climb is typically at, or slightly above Mcrit.
I mentioned Super Critical Wing because these aircraft have a much lower rate of Wave drag rise for the earlier stages of Mcrit exceedance, thus the .02 to .03 that I mentioned will probably be somewhat higher for these aircraft.
Don't fall into the trap that Mcrit represents a speed limit on the aircraft, it is the Mach Number at which the first shock waves begin to form, after which wave drag rises. Also it is the speed beyond which some of the undesirable characteristics of high speed flight first appear (Mach Tuck etc.), but these are managable somewhat beyond Mcrit, where jet transport aircraft operate every day. As these undesirable characteristics increase to unacceptable levels, MMO is imposed, with suitable margins of course.
Regards,
Old Smokey
A bit uncomfy operating above Mcrit ? You'd better get used to it, ALL cruise Mach Numbers are above Mcrit, even Maximum Range Cruise, the lowest en-route speed that you'd ever want to fly. Similarly, the Mach Number phase of descent is typically above Mcrit, unless you've opted for the Maximum Range Descent which tends to be somewhat slower. Climb is typically at, or slightly above Mcrit.
I mentioned Super Critical Wing because these aircraft have a much lower rate of Wave drag rise for the earlier stages of Mcrit exceedance, thus the .02 to .03 that I mentioned will probably be somewhat higher for these aircraft.
Don't fall into the trap that Mcrit represents a speed limit on the aircraft, it is the Mach Number at which the first shock waves begin to form, after which wave drag rises. Also it is the speed beyond which some of the undesirable characteristics of high speed flight first appear (Mach Tuck etc.), but these are managable somewhat beyond Mcrit, where jet transport aircraft operate every day. As these undesirable characteristics increase to unacceptable levels, MMO is imposed, with suitable margins of course.
Regards,
Old Smokey
Thread Starter
Join Date: Nov 2002
Location: Everywhere
Posts: 108
Likes: 0
Received 0 Likes
on
0 Posts
I believe the Mach Trimmer comes in at M.615 and above on the 737-400.
Flying above the Mcrit where first shock waves are formed locally on the airplane can be a bit uncomfy for the passengers i reckon.
Flying above the Mcrit where first shock waves are formed locally on the airplane can be a bit uncomfy for the passengers i reckon.
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
Hachiouji-shi,
You're starting to get me a bit worried. The B737 is not exactly the fastest thing on wings, but Mcrit would be well above M0.615, that would 'Max out' the 'useful' cruise at about M0.65. I recall that it's about M0.72 to M0.73, but it's 23 years since I last flew a B737-300.
Why would flying above Mcrit be a bit uncomfy for the passengers? They wouldn't even notice it! I've operated about 16,000 flights on jets above Mcrit and I haven't noticed it yet, maybe I'm a slow learner.
Actually, I have to take a step back, and say that they MIGHT notice it - visually. If you have a wing seat, the sun is low in the sky, and you're looking along the wing in the general direction of the sun, the shock waves can be highly visible, and very pretty to watch. They don't let us fly fast enough these days to see the big beauties that we saw on the B707, but, in the right seat with the sun at the right angle, you might still see the occasional itty-bitty fuel economical shock waves of our times.
Regards,
Old Smokey
You're starting to get me a bit worried. The B737 is not exactly the fastest thing on wings, but Mcrit would be well above M0.615, that would 'Max out' the 'useful' cruise at about M0.65. I recall that it's about M0.72 to M0.73, but it's 23 years since I last flew a B737-300.
Why would flying above Mcrit be a bit uncomfy for the passengers? They wouldn't even notice it! I've operated about 16,000 flights on jets above Mcrit and I haven't noticed it yet, maybe I'm a slow learner.
Actually, I have to take a step back, and say that they MIGHT notice it - visually. If you have a wing seat, the sun is low in the sky, and you're looking along the wing in the general direction of the sun, the shock waves can be highly visible, and very pretty to watch. They don't let us fly fast enough these days to see the big beauties that we saw on the B707, but, in the right seat with the sun at the right angle, you might still see the occasional itty-bitty fuel economical shock waves of our times.
Regards,
Old Smokey
Thread Starter
Join Date: Nov 2002
Location: Everywhere
Posts: 108
Likes: 0
Received 0 Likes
on
0 Posts
I will keep posts related to initial topic.
So for now, on the 737 its approximately equal to your Climb Mach No., or your Long Range Cruise Mach No. minus 0.02 or 0.03. Ok thanks everybody.
So for now, on the 737 its approximately equal to your Climb Mach No., or your Long Range Cruise Mach No. minus 0.02 or 0.03. Ok thanks everybody.
Join Date: Apr 2002
Location: UK
Posts: 386
Likes: 0
Received 0 Likes
on
0 Posts
I do think the Mach Trimmer works from 0.615M onwards, because you can dispatch with the thing U/S with this speed limitation imposed onto it.
And I remember that number from doing the Tech Course.
So it makes interesting reading.
Having flown the 73 300 & 700 (-700 having a redesigned wing) typical cruise mach on the -300 is 0.74 but flies happily along at 0.79 albeit not at econ cruise alt.
the -700 wing is made for 38000/39000' at M0.78 with Mmo0.82
And I remember that number from doing the Tech Course.
So it makes interesting reading.
Having flown the 73 300 & 700 (-700 having a redesigned wing) typical cruise mach on the -300 is 0.74 but flies happily along at 0.79 albeit not at econ cruise alt.
the -700 wing is made for 38000/39000' at M0.78 with Mmo0.82
Join Date: Oct 2005
Location: Over there
Posts: 28
Likes: 0
Received 0 Likes
on
0 Posts
I do think the Mach Trimmer works from 0.615M onwards, because you can dispatch with the thing U/S with this speed limitation imposed onto it.
Join Date: Sep 1999
Location: ME
Posts: 5,505
Likes: 0
Received 0 Likes
on
0 Posts
Hachiouji-shi
You want to keep to the original subject... No problem... Please tell us WHAT YOU think the CRITICAL MACH NUMBER is used for?
You have gotten an excellent response from Old_smokey.
Mutt
You want to keep to the original subject... No problem... Please tell us WHAT YOU think the CRITICAL MACH NUMBER is used for?
You have gotten an excellent response from Old_smokey.
Mutt
Join Date: Jun 2004
Location: Australia
Posts: 1,843
Likes: 0
Received 0 Likes
on
0 Posts
CaptainSandL, "If it helps, Mach buffet onset occurs at between 0.815 & 0.825 on the classics & at a speed beyond Mmo on the NG's."
Yes, every little bit helps in putting this jig-saw puzzle together, piece by piece we're putting this puzzle together until someone comes up with the correct figure for the aircraft.
What you've demonstrated here (as I'm sure you're aware) are the undesirable aerodynamic characteristics which become obvious, and unacceptable somewhat AFTER Mcrit has been exceeded, as indicated in my earlier remarks - "......the speed beyond which some of the undesirable characteristics of high speed flight first appear (Mach Tuck etc.), but these are managable somewhat beyond Mcrit, where jet transport aircraft operate every day. As these undesirable characteristics increase to unacceptable levels, MMO is imposed, with suitable margins of course.
Does anyone have any more pieces to the B737 Mcrit puzzle?
Regards,
Old Smokey
Yes, every little bit helps in putting this jig-saw puzzle together, piece by piece we're putting this puzzle together until someone comes up with the correct figure for the aircraft.
What you've demonstrated here (as I'm sure you're aware) are the undesirable aerodynamic characteristics which become obvious, and unacceptable somewhat AFTER Mcrit has been exceeded, as indicated in my earlier remarks - "......the speed beyond which some of the undesirable characteristics of high speed flight first appear (Mach Tuck etc.), but these are managable somewhat beyond Mcrit, where jet transport aircraft operate every day. As these undesirable characteristics increase to unacceptable levels, MMO is imposed, with suitable margins of course.
Does anyone have any more pieces to the B737 Mcrit puzzle?
Regards,
Old Smokey
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
I'm still not sure that Hachiouji-shi actually understands what you have been saying, OS?
H-S - Mcrit is when the FIRST shockwave forms on an AIRCRAFT - on any part. It has nothing to do with Mach buffet or MMo, climb or cruise speeds.
For Old Smokey, my piece of the jigsaw is that I STILL believe the cockpit roof on a 737 is where Mcrit 'happens'
H-S - Mcrit is when the FIRST shockwave forms on an AIRCRAFT - on any part. It has nothing to do with Mach buffet or MMo, climb or cruise speeds.
For Old Smokey, my piece of the jigsaw is that I STILL believe the cockpit roof on a 737 is where Mcrit 'happens'