Iloveboeing
Topic Author
Posts: 428
Joined: Mon Oct 31, 2005 11:02 am

### Can The 777 Cruise At Mach 0.85?

I was wondering if the 777 can cruise at Mach 0.85, like the 747 and 787? Boeing lists the typical cruise at Mach 0.84 on their website, but, in the past, I've heard them claim that the 787 will cruise at Mach 0.85, similar to the cruising speed of the 747 and 777, so I was wondering if normal cruise for the 777 could be Mach 0.85. Thanks!

Mir
Posts: 19491
Joined: Mon Jan 05, 2004 3:55 am

### RE: Can The 777 Cruise At Mach 0.85?

It could certainly cruise at .85, but you'd be losing a lot more in efficiency than you'd be gaining in speed.

 Quoting Iloveboeing (Thread starter):in the past, I've heard them claim that the 787 will cruise at Mach 0.85, similar to the cruising speed of the 747 and 777

The 777's normal cruise is .84. The difference between .84 and .85 is only about 10kts on average, so it is fair to say that the 787 has a similar cruising speed to the 777 (though it is a bit faster).

-Mir
7 billion, one nation, imagination...it's a beautiful day

zeke
Posts: 14402
Joined: Thu Dec 14, 2006 1:42 pm

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting Iloveboeing (Thread starter):Boeing lists the typical cruise at Mach 0.84 on their website, but, in the past, I've heard them claim that the 787 will cruise at Mach 0.85, similar to the cruising speed of the 747 and 777, so I was wondering if normal cruise for the 777 could be Mach 0.85. Thanks!

The 777 can cruise at the same speed as the 744, but it would be using more fuel than normal if they both departed the same point along the same route.

In our airline we do not use a constant mach number for cruise, it varies with the cost index selected in the FMC, altitude, and weight. The 744 for example will cruise anywhere from 0.83 to 0.85 FL330-FL360.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

mandala499
Posts: 6592
Joined: Wed Aug 29, 2001 8:47 pm

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting Iloveboeing (Thread starter):so I was wondering if normal cruise for the 777 could be Mach 0.85.

I got a friend who is dyslexic whenever he sees the CI input on the FMC... 150 instead of 051... He also goes 0.85 often...   The funny thing is, he burns less fuel... *bangs head on table* The last part of my comment can be taken as a wind up...
When losing situational awareness, pray Cumulus Granitus isn't nearby !

Zkpilot
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Joined: Wed Mar 08, 2006 8:21 pm

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting Zeke (Reply 2):n our airline we do not use a constant mach number for cruise, it varies with the cost index selected in the FMC, altitude, and weight. The 744 for example will cruise anywhere from 0.83 to 0.85 FL330-FL360.

Most airlines operate in this manner... more cost effective.
Just been on a flight with a decent tailwind... 1100km/h g/s (584kt and about 0.92mach approx g/s lol) in a 763. Normal 3 hour trip was done in 2 hours
64 types. 44 countries. 24 airlines.

CX Flyboy
Posts: 6133
Joined: Sun Dec 26, 1999 6:10 pm

### RE: Can The 777 Cruise At Mach 0.85?

I've done Mach 0.88 before, diverting in a medical emergency.

RJdxer
Posts: 3523
Joined: Thu Nov 09, 2006 1:14 am

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting Zkpilot (Reply 4):Most airlines operate in this manner... more cost effective.

But a factor is also time. If cruising at .85 will make up enough minutes without dramatically upping the burn, you would be expected to get the flight there on time. There are several ways to accomplish this besides crz at .85
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KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting CX flyboy (Reply 5):I've done Mach 0.88 before, diverting in a medical emergency.

Is that close to the Mmo speed?
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tito
Posts: 122
Joined: Sat Feb 17, 2001 1:39 pm

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting Zeke (Reply 2):In our airline we do not use a constant mach number for cruise, it varies with the cost index selected in the FMC, altitude, and weight. The 744 for example will cruise anywhere from 0.83 to 0.85 FL330-FL360

...and don't forget wind too. FMC will increase cruise mach number with a headwind.

zeke
Posts: 14402
Joined: Thu Dec 14, 2006 1:42 pm

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting Tito (Reply 8):..and don't forget wind too. FMC will increase cruise mach number with a headwind.

And decrease with a tailwind.....
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

kimberlyRJ
Posts: 249
Joined: Thu Mar 06, 2008 7:35 am

### RE: Can The 777 Cruise At Mach 0.85?

Hello

I work on both the Boeing 747 & Boeing 777 and the B744 always flies faster then the B772 as far as I have seen. Sometimes when returning from North American to the UK when we have a nice tail wind we sometimes get to M.85 but it’s not as often as the B744.

Regards

Kimberly

CX Flyboy
Posts: 6133
Joined: Sun Dec 26, 1999 6:10 pm

### RE: Can The 777 Cruise At Mach 0.85?

 Quoting KELPkid (Reply 7):Is that close to the Mmo speed?

Mach 0.89 is the MMO, so yes it was close. Ok in smooth air but you wouldn't want to cruise at that in turbulence.

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