A330-900 Cruise Mach
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A330-900 Cruise Mach
Hello everyone!
Would anyone care to tell me the typical (optimum weight and optimum altitude) cruise Mach number for the A330-900?
From my A330-200 days I (seem to) remember around M.812. If we were in a hurry we could go M.815 to M.817 without worrying too much about fuel burn.
Would anyone have equivalent Mach numbers for the A339?
So far I have seen video clips with numbers similar to the A332, but also twice (on two different carriers) M.827, which is not what I remember doing on the MMO.84 A332 too often.
Thank you for reading and taking the time to respond.
B.
Would anyone care to tell me the typical (optimum weight and optimum altitude) cruise Mach number for the A330-900?
From my A330-200 days I (seem to) remember around M.812. If we were in a hurry we could go M.815 to M.817 without worrying too much about fuel burn.
Would anyone have equivalent Mach numbers for the A339?
So far I have seen video clips with numbers similar to the A332, but also twice (on two different carriers) M.827, which is not what I remember doing on the MMO.84 A332 too often.
Thank you for reading and taking the time to respond.
B.
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From: USA
(should that be 5 millimachs?)
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From: GPS L INVALID
Jesus, your plane can maintain +- 0.001 Mach? Secondly, accelerating from .812 to .815 would maybe save you perhaps half a minute on an eight hour segment, are you sure we are talking about the correct orders of magnitude here?
(I agree with check airman, we are henceforth talking about millimach)
(I agree with check airman, we are henceforth talking about millimach)
Last edited by STBYRUD; 4th December 2025 at 06:28.
Thread Starter
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From: Portugal
I admit, this question was primarily aimed at the pros who move airplanes like A330s and 777s around in the sky and is largely academic.
I may not have ‘check airman’ in my user name, but training and checking is what I used to do on A330s and A340s and you learned (and taught) to pay attention to details (like the difference in fuel burn between M.805 or M.815)
To put this into relation, at M.80 the A332 burned (at 220 tons and F350) 6,106 kgs/hr at M.82 and 6,354 kg/hr (for those not at home in the metric system 485,000 lb and 13,461 lb/hr and 14,000 lb/hr respectively), a difference of 4%.
The difference between M.805 and M.815 at F350 is 6 nautical miles an hour, so making 5 minutes on an 8 hr (maybe twice that when actively requesting shortcuts) was not earth shattering but also nothing to scoff at.
Not huge, but if you left late and made up some of the delay (for connecting passengers) for hardly any increase in fuel burn and without eating into your 6% contingency fuel that was a question of professional pride.
Of course, any idiot could increase from M.812 to M.83, (my apologies, the correct MMO on out A332s was M.86 not M.84, as stated in my OP), but these guys tended to go pale when they had used up their contingency and were told at destination to hold for 15 mins.
Agreed, largely academic, but I was curious what the tweaks on the A339/A338 wing did to the Econ Cruise Mach Number that, according to Airbus, increased slightly.
B.
I may not have ‘check airman’ in my user name, but training and checking is what I used to do on A330s and A340s and you learned (and taught) to pay attention to details (like the difference in fuel burn between M.805 or M.815)
To put this into relation, at M.80 the A332 burned (at 220 tons and F350) 6,106 kgs/hr at M.82 and 6,354 kg/hr (for those not at home in the metric system 485,000 lb and 13,461 lb/hr and 14,000 lb/hr respectively), a difference of 4%.
The difference between M.805 and M.815 at F350 is 6 nautical miles an hour, so making 5 minutes on an 8 hr (maybe twice that when actively requesting shortcuts) was not earth shattering but also nothing to scoff at.
Not huge, but if you left late and made up some of the delay (for connecting passengers) for hardly any increase in fuel burn and without eating into your 6% contingency fuel that was a question of professional pride.
Of course, any idiot could increase from M.812 to M.83, (my apologies, the correct MMO on out A332s was M.86 not M.84, as stated in my OP), but these guys tended to go pale when they had used up their contingency and were told at destination to hold for 15 mins.
Agreed, largely academic, but I was curious what the tweaks on the A339/A338 wing did to the Econ Cruise Mach Number that, according to Airbus, increased slightly.
B.
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From: Blue sky
That being said, back then I was involved with a company that changed from decades of Boeing to all Airbus. Engineering and pilots loved to bash that decision. I'll admit I've always been keen to see exact numbers to support that statement.
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Maybe the question comes from what I was told in early engineering days that the Airbus wing was very efficient, but only close to the design point. Change speed, and you would pay the price. The Boeing wings gave much more flexibility in the speed range.
That being said, back then I was involved with a company that changed from decades of Boeing to all Airbus. Engineering and pilots loved to bash that decision. I'll admit I've always been keen to see exact numbers to support that statement.
That being said, back then I was involved with a company that changed from decades of Boeing to all Airbus. Engineering and pilots loved to bash that decision. I'll admit I've always been keen to see exact numbers to support that statement.
That is certainly true for earlier Boeings, but the 777 has less speed flexibility than the A330/A340s. The 777’s ‘sweet spot’ is around M.835 to M.84.
If you were at optimum altitude and as long as you stayed in that range, fuel economy was at its best.
But unlike the Busses, the 777 did not care much for M.82 unless you were kept low; in that sense the 777 wing design more “peaky’ than the A330s and A340s.
When I picked up a new 777 from Everett, we used to cruise part of the trip at M.86, to get data points at various speeds to verify contractual performance.
Not a speed you would want to do in line ops (€€€€/$$$$).
Yes, pilots and engineers used to love bashing Airbuses, but that was when Boeing was still an ‘engineering driven’ rather than the ‘stockholder value driven’ company that it became under McDonell-Douglas top management.
Many inside the industry believe that the 777 was Boeing’s ‘last hurrah’ and that they have a long and arduous way ahead of them. (See also: Scott Hamilton, The Rise and Fall of Boeing and The Way Back,)
B.
Last edited by Brutus53; 4th December 2025 at 09:45.
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From: GPS L INVALID
I'm sorry, but do you have any (non-anecdotal) evidence to back any of this up? The FPPMs certainly do not confirm this, and there must be a reason why most airlines fly econ speeds based on cost indices... Apparently I'm not in the pro league, so please enlighten me.
Joined: Mar 2006
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From: USA
I admit, this question was primarily aimed at the pros who move airplanes like A330s and 777s around in the sky and is largely academic.
I may not have ‘check airman’ in my user name, but training and checking is what I used to do on A330s and A340s and you learned (and taught) to pay attention to details (like the difference in fuel burn between M.805 or M.815)
To put this into relation, at M.80 the A332 burned (at 220 tons and F350) 6,106 kgs/hr at M.82 and 6,354 kg/hr (for those not at home in the metric system 485,000 lb and 13,461 lb/hr and 14,000 lb/hr respectively), a difference of 4%.
The difference between M.805 and M.815 at F350 is 6 nautical miles an hour, so making 5 minutes on an 8 hr (maybe twice that when actively requesting shortcuts) was not earth shattering but also nothing to scoff at.
Not huge, but if you left late and made up some of the delay (for connecting passengers) for hardly any increase in fuel burn and without eating into your 6% contingency fuel that was a question of professional pride.
Of course, any idiot could increase from M.812 to M.83, (my apologies, the correct MMO on out A332s was M.86 not M.84, as stated in my OP), but these guys tended to go pale when they had used up their contingency and were told at destination to hold for 15 mins.
Agreed, largely academic, but I was curious what the tweaks on the A339/A338 wing did to the Econ Cruise Mach Number that, according to Airbus, increased slightly.
B.
I may not have ‘check airman’ in my user name, but training and checking is what I used to do on A330s and A340s and you learned (and taught) to pay attention to details (like the difference in fuel burn between M.805 or M.815)
To put this into relation, at M.80 the A332 burned (at 220 tons and F350) 6,106 kgs/hr at M.82 and 6,354 kg/hr (for those not at home in the metric system 485,000 lb and 13,461 lb/hr and 14,000 lb/hr respectively), a difference of 4%.
The difference between M.805 and M.815 at F350 is 6 nautical miles an hour, so making 5 minutes on an 8 hr (maybe twice that when actively requesting shortcuts) was not earth shattering but also nothing to scoff at.
Not huge, but if you left late and made up some of the delay (for connecting passengers) for hardly any increase in fuel burn and without eating into your 6% contingency fuel that was a question of professional pride.
Of course, any idiot could increase from M.812 to M.83, (my apologies, the correct MMO on out A332s was M.86 not M.84, as stated in my OP), but these guys tended to go pale when they had used up their contingency and were told at destination to hold for 15 mins.
Agreed, largely academic, but I was curious what the tweaks on the A339/A338 wing did to the Econ Cruise Mach Number that, according to Airbus, increased slightly.
B.
I can see 0.01 making a difference on a long flight. 0.001 is academic IMO. I’m on the 777, and I’ve never seen anyone adjust speed by less than a hundredth.
Can the A330 even accept the third decimal?
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From: Portugal
Thread Starter
Joined: Jan 2025
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From: Portugal
Here you’re talking about a difference of a hundredth, but the first post talks about thousandths.
I can see 0.01 making a difference on a long flight. 0.001 is academic IMO. I’m on the 777, and I’ve never seen anyone adjust speed by less than a hundredth.
Can the A330 even accept the third decimal?
I can see 0.01 making a difference on a long flight. 0.001 is academic IMO. I’m on the 777, and I’ve never seen anyone adjust speed by less than a hundredth.
Can the A330 even accept the third decimal?
Most commonly, however, I played with the Mach number through manipulating the CI.
I found it a useful exercise (but that’s me); nail the Mach number through the FCU and then play with the CI to see how much time one could make and how much fuel it would cost.
Think of it as playtime on long Atlantic/Indian Ocean crossings.
B.
Last edited by Brutus53; 4th December 2025 at 17:29.
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Maybe this will help.
(I don’t have access to either FPPM and primarily used FCOMs, FCTMs and AFMs.)
You are of course entirely right; airlines operate with Cost Index (CI) based speeds, but as time-related costs vary from airline to airline (and some airlines consider some costs time-related that another may consider fixed) and fuel prices vary from airport to airport, the somewhat antiquated LRC, that tends to follow as similar trend as CI speeds, is still used for such comparisons.
Looking at LRC (defined as 99% of maximum range on jets) and typical early cruise weights you get this:
Mach Number 4000 ft below opt/ opt/ 2000 ft above opt (opt = FL350)
Altitude FL310/ FL350/ FL370
A330-200 220 tons M.799/ M.816/ M.819
777-300ER 260 tons M.828/ M.840/ M.838
Specific Range Change
(NM/1000kg)
Altitude FL310/ FL350/ /FL370
A330-200 220 tons. -2.4%/ 0/ -2.2%
777-300ER 260 tons -3.9%/ 0/ -2.6%
To me, it indicates that the 777 speed varies less than the A330 in Mach number when operating ‘off’ optimum altitude, but varies more in specific range.
I take that to mean that the 777 was designed more around a specific Mach number than the A330.
(If you have access to an old fashioned AFM with Cruise Maneuver Capability graphs, this usually coincides at higher weights with the Mach number at which the Cruise Maneuver capability peaks.)
Of course, these are only spot values and one should not read too much in them.
(Apologies for the changes in formatting.)
B.
Last edited by Brutus53; 4th December 2025 at 18:49.
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I was en route somewhere, out for a bathroom stop and a guy asked me if I liked flying the A330 - I said, yep - brilliant aeroplane. Oh, good said he, I was on the wing design team and my son in law is in the development team.....
Poked my head back in the office and said - I may be some time !!!!!
Primary question was - what was the wing designed to cruise at ?
.82
What happens if you cruise at .79 ?
You burn more fuel because of trim drag.
Why are the trailing edges so blunt ?
Because of laminar flow projection which gives an apparent chord increase which increases efficiency.
What a fascinating man.... His son was working on single skin changeable wings with no joints or separate flaps.
A great 30 mins of ejumacashun !
Poked my head back in the office and said - I may be some time !!!!!
Primary question was - what was the wing designed to cruise at ?
.82
What happens if you cruise at .79 ?
You burn more fuel because of trim drag.
Why are the trailing edges so blunt ?
Because of laminar flow projection which gives an apparent chord increase which increases efficiency.
What a fascinating man.... His son was working on single skin changeable wings with no joints or separate flaps.
A great 30 mins of ejumacashun !
Thread Starter
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From: Portugal
Much appreciated..
Just one question: is the CI that you quoted metric (KG/MIN) or imperial (100 lb/hr)?
On the A332 the CI to approximate LRC was 40 (KG/MIN) or 53 (100 lb/hr).
B.
Last edited by Brutus53; 6th December 2025 at 09:24.
Thread Starter
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From: Portugal
I was en route somewhere, out for a bathroom stop and a guy asked me if I liked flying the A330 - I said, yep - brilliant aeroplane. Oh, good said he, I was on the wing design team and my son in law is in the development team.....
Poked my head back in the office and said - I may be some time !!!!!
Primary question was - what was the wing designed to cruise at ?
.82
What happens if you cruise at .79 ?
You burn more fuel because of trim drag.
Why are the trailing edges so blunt ?
Because of laminar flow projection which gives an apparent chord increase which increases efficiency.
What a fascinating man.... His son was working on single skin changeable wings with no joints or separate flaps.
A great 30 mins of ejumacashun !
Poked my head back in the office and said - I may be some time !!!!!
Primary question was - what was the wing designed to cruise at ?
.82
What happens if you cruise at .79 ?
You burn more fuel because of trim drag.
Why are the trailing edges so blunt ?
Because of laminar flow projection which gives an apparent chord increase which increases efficiency.
What a fascinating man.... His son was working on single skin changeable wings with no joints or separate flaps.
A great 30 mins of ejumacashun !
I’d loved talking to that guy too.
You can gain quite a few insights form chats like that, even if it is (like a speed increase of Mach zero point zero zero whatever 😏 ) strictly nice to know stuff.
Before we got our first A330-200 (we were not the launch customer, but pretty close behind) we had one of the Airbus test pilots deliver a lecture about the A330 in general and the new 200 variant in particular dubbed “Why we built it the way we did” (or something to that effect).
That was a treasure trove of information and helped you understand the airplane and why it sometimes did what it did.
It seemed that Airbus had by then learned how important it was to cultivate the relationship with pilots, a lesson that Boeing forgot a few years later under McDonnell Douglas management, when they discontinued the beloved Airliner magazine that for decades had helped pilots understand their airplanes.
B.
Last edited by Brutus53; 6th December 2025 at 10:25.
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From: Feet on the rudder pedals
These values are metric. Currently flying the A339, I confirm LRC's metric cost index is 90.
