brons2
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What Is Vmo On The 73G?

Sat Aug 22, 2009 5:48 am

I was reading an incident report at the NTSB site:

http://www.ntsb.gov/ntsb/brief2.asp?...112X35356&ntsbno=DCA09WA023&akey=1

Which notated that the 73G involved in the incident exceeded Vmo by 100 kts. Just wondering what Vmo is on the plane in question.

...and for that matter, while we're on the subject, what is the Vne of the 73G? I wonder how much they exceeded that by??
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rwessel
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RE: What Is Vmo On The 73G?

Sat Aug 22, 2009 6:30 am

For a 737-700, Vmo is 340kts. The 737 is a transport category jet - it has no published Vne as such. Vmo (along with Mmo) is the closest number available, and serves basically the same purpose.

edit: Mmo parenthetical added

[Edited 2009-08-21 23:35:13]
 
wilco737
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RE: What Is Vmo On The 73G?

Sat Aug 22, 2009 10:15 am



Quoting Rwessel (Reply 1):
737-700,

For all 737 models I flew (300/500/700/800) the Vmo is 340 kts and the Mmo was M0.82. But the A/T didn't let you go that fast. At M0.817 he stopped  Wink

wilco737
 
tdscanuck
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RE: What Is Vmo On The 73G?

Sat Aug 22, 2009 4:34 pm



Quoting Rwessel (Reply 1):
For a 737-700, Vmo is 340kts. The 737 is a transport category jet - it has no published Vne as such. Vmo (along with Mmo) is the closest number available, and serves basically the same purpose.

There is no Vmo, but there is a Vd (and Md), which is the closest equivalent. You're never supposed to fly there, but you need to know what it is for certification. For some reason, it's not shown in the AFM though.

Tom.
 
aeroweanie
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RE: What Is Vmo On The 73G?

Sat Aug 22, 2009 9:48 pm



Quoting Tdscanuck (Reply 3):
There is no Vmo, but there is a Vd (and Md), which is the closest equivalent. You're never supposed to fly there, but you need to know what it is for certification. For some reason, it's not shown in the AFM though.

Interestingly enough, except for the 767 (A1NM) and A330 (A46NM), Vd/Md is also not listed in the FAA Type Certificate Data Sheet. You can calculate the minimum Vd/Md using the appropriate regulations, but sometimes aircraft (such as the DC-10) are certified to higher values of Vd/Md.
 
wilco737
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RE: What Is Vmo On The 73G?

Sun Aug 23, 2009 1:33 am



Quoting Tdscanuck (Reply 3):
There is no Vmo, but there is a Vd (and Md),

We used both names and speeds, but for the daily operation we used Vmo and Mmo.

wilco737
 
tdscanuck
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RE: What Is Vmo On The 73G?

Sun Aug 23, 2009 1:58 am



Quoting Tdscanuck (Reply 3):
There is no Vmo, but there is a Vd (and Md)

Sorry, that should have read "There is no *Vne*, but there is a Vd (and Md)."

Tom.
 
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tb727
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RE: What Is Vmo On The 73G?

Sun Aug 23, 2009 2:46 am

Interesting, sounds like they experienced Mach Tuck.
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brons2
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RE: What Is Vmo On The 73G?

Sun Aug 23, 2009 6:15 am



Quoting Tb727 (Reply 7):
Interesting, sounds like they experienced Mach Tuck.

If so, how did they recover it? More drag at a lower altitude?

This seems like a pretty radical excursion from controlled flight to me. Glad everyone is ok.
Firings, if well done, are good for employee morale.
 
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tb727
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RE: What Is Vmo On The 73G?

Sun Aug 23, 2009 4:28 pm



Quoting Brons2 (Reply 8):
If so, how did they recover it? More drag at a lower altitude?

Yeah more than likely that is what happened, more drag slowed it down. If you get into a situation when you start messing with mach tuck, you have to get it slowed down. It was especially critical in the Learjet, I've hit a mountain wave in which we hit Mach 0.84, which is dangerously close to mach tuck in that thing. We brought the throttles to idle and hoped for the best because it still wasn't slowing down.

I'm not implying any wrong doing on this 737, but there were only 4 crew members on board, I'm thinking maybe they were seeing how fast they could get it to go since they were empty. Is there anything else on this incident?
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Max Q
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RE: What Is Vmo On The 73G?

Wed Aug 26, 2009 12:38 am

Quoting Tb727 (Reply 9):

I'm not implying any wrong doing on this 737, but there were only 4 crew members on board, I'm thinking maybe they were seeing how fast they could get it to go since they were empty. Is there anything else on this incident?

The reason there were only 4 crew members on board is because it was a maintenance test flight.


They were not 'seeing how fast it would go' they were accomplishing a planned procedure to test 'manual reversion' of the flight controls.


Because of a prior maintenance misrigging error when they turned off the hydraulics to the flight controls the Aircraft entered a violent pitch down during which they inadvertently did exceed VMO by 100 knots.


It is a great testamant to the skill of the Pilots and the rugged Boeing design they were able to recover.
.

[Edited 2009-08-25 17:39:49]
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