MTOW and RTOW

[beinghuman]

Hello Guys,

Can you'll explain the difference between MTOW and RTOW while calculating ?

For example Airbus A320 has a MTOW of 73500 Kg.

If the question asks about the MTOW. Calculating and considering all the QNH, AC and other corrections, if the Max take off weight comes to 78500 kg. What is my RTOW and MTOW here ?

I was checking an F'COM and the examples to calculate the MTOW, left the answer at 78500 kg. Shouldn't it be 73500 kg cause that's the max we can carry anyway ? Little confused here.

Thanks in advance :)

[de facto]

The MTOW is your Structural max take off weight(real weight).
The RTOW (Regulated) is your Performance adjusted take off weight which must be below your runway/obstacle level off/climb limit weight.

The adjustments are qnh,bleeds OFf,EAI ON.....
On a long runway you could see that your RTOW limit is well above your MTOW,up to 82T for a 738.

[john_tullamarine]

Depends on how you do the sums from the AFM.

MTOW is a hard limit regardless of other considerations and is tied up with the basic aircraft certification basis.

RTOW is the limiting takeoff weight calculated for a particular runway under particular specified conditions.

Generally, though, the published RTOW will be truncated for other limiting considerations for convenience.

Usually the only time you might see a performance weight greater than MTOW will be in relation to climb limits where the calculated figure is given to facilitate interpolation - it doesn't make much sense to interpolate between figures where one has already been truncated due to other limits. In this situation the interpolated figure then is compared to other limits in the normal manner to determine the overall limiting figure.

Either way, the authorised TOW will not exceed the MTOW (unless per Regulatory one-off approval as, for instance, may occur for ferry operations).

[parabellum]

Just remember, when applying weight penalties for take off due some unserviceability, like anti-skid U/S, for instance, that the penalty comes off the WATlimit for that runway, (Weight, Altitude & Temperature), which can be well in excess of the MTOW and does not come off the MTOW unless otherwise stated in the AFM.

Saw a flight cancelled once because the penalty was applied to the MTOW and not the WAT limit, when the WAT limit was well in excess of the MTOW and a max weight take off was possible, subject to landing performance of course, which in this case was an even longer runway!

[Denti]

MTOW is a hard limit regardless of other considerations and is tied up with the basic aircraft certification basis.

In general true, however for stuff like airway or landing fees the MTOW can be flexible again. We use around 8 to 10 different MTOWs and select the lowest usable for each flight. That MTOW is then the basis for all kind fees associated with that flight. The highest usable one is the certified one, which does not necessarily have to be the structural limit, some of our 738 have around 75t, others over 78t. Just a matter of certified max weight which can be changed whenever there is any need.

[john_tullamarine]

That's the first time I've heard of that approach. In my experience, Regulators have been amenable to a permanent reduction in AFM MTOW for this reason .. but not one which, in your story, appears to change by the flight ?

Could we have a bit more of the story, please ?

[ironbutt57]

@parabellum, not an uncommon mistake...PERFORMANCE penalties are deducted from the PERFORMANCE limiting weight..RTOW....easy way to avert the error you witnessed...

[Capt Claret]

B717, MTOW 53,525 kg.

RTOW values can be in the mid 54s or better.

A CDL/MEL performance degradation would be subtracted from the RTOW value, thus in many cases, MTOW may not be affected even though there is a performance penalty.

[Capn Bloggs]

We use around 8 to 10 different MTOWs and select the lowest usable for each flight.
Agree JT, this sounds a bit dodgy. Denti, do you mean that you have 8-10 aeroplanes with different MTOWs or one aeroplane with 8-10 MTOWs? My employer has done this in the past, but the reduced MTOW (one only) was promulgated in the AFM and not changed at the drop of a hat. Obviously though, the cost of doing so was made up in reduced landing fees.

[763 jock]

My company also does this. We have a declared (767) weight that is about 25000 kgs below the structural max. This is done to reduce landing fees etc.

If they then need the higher weight for long haul ops, they declare it on the day.

[john_tullamarine]

I guess no reason why not .. other than the airport owners and airways folk who are losing dollars. Intriguing way of moving the walnuts around.

[172_driver]

My airline also has a flexible MTOW system to reduce fees. Three different settings on the B738. As late as yesterday landed with one MTOW and departed with another. A maintenance action required during turnaround, takes 2 min.

[john_tullamarine]

I'm utterly amazed that the bean counters in the service organisations have let that happen. I guess that the Industry, eventually, will bear little resemblance to what it was 30-50 years ago.

[Capn Bloggs]

I'm utterly amazed that the bean counters in the service organisations have let that happen. I guess that the Industry, eventually, will bear little resemblance to what it was 30-50 years ago.
That's what you get when those with degrees in "underwater basket weaving" take over.

Changing MTOWs in 2 minutes to avoid landing fees. I love it! :D

[alf5071h]

IIRC, operators are not allowed to chop and change MTOW to alleviate airport fees.
This may be an old interpretation (UKCAA / JAA days), but way back operators could apply for one change (a reduction) in MTOW which resulted in adding an amendment to the AFM. This became the legal MTOW for landing fees etc. An airport etc could ask to see the AFM, and the landing fees charged accordingly.
There should be JAR / EASA guidance on the issue somewhere.

[john_tullamarine]

Now, that story I prefer and is consistent with a number of Oz aircraft whose AFMs were amended by my good self for just that purpose.

[Don Coyote]

Details of VMTOW found at http://www.caa.co.uk/docs/33/FOD200920.pdf

[oceancrosser]

I was recently told that Eurocontrol is dropping the flex weight charging and will charge based on the actual highest MTOW of the particular aircraft, and that a lot of European airports are moving towards same.
Hence the benefits of the flex weights are eroding in the EASA area.

[john_tullamarine]

Obviously the UK was more innovative than other Regulators. Quite amazing.

[Denti]

Actually, we are not governed by the UK CAA, just another european CAA. Funny enough, there are a couple airplanes in our fleet that do not have flex MTOWs, for those we always have to use the actual MTOW, from what i remember those were not build for us and are leased in from external sources.

About AFMs, there is none on board anymore, the EFB contains a generic AFM for the 737, but not specific for the airplane in question, the AFM is not part of the normally used documentation anyway. There might be a storage space somewhere in the headquarter for all those original AFMs, but somehow i doubt it.

I guess as soon as there can be no money saved by the flex weight thing the company gonna drop it, as the administration of the whole thing costs money too.

[gorter]

I work for a uk operator that does have flexible MTOW, but I was always under the impression (from my ops department) that it would take 2-3 working days to have the requisite approvals to change a MTOW. Having it change from inbound to outbound is impressive.

[beinghuman]

So for theory purpose, if your take off weight calculation comes to 78500 kgs after all the corrections for Airbus A320. Considering your Max TOW limit as 73500 kgs for A320, what would be your MTOW ?

You'd say your MTOW is 78500 or 73500 ? (Again, for theory purpose only)

Thanks folks.

[Tagron]

beinghuman

I suspect perhaps you are being confused by terms and definitions.

Regulated Take off Weight is the maximum weight at which you can perform a particular take-off. It is the lesser of the calculated performance limited weight and the aircraft's certificated MTOW. In the case you quote, the MTOW becomes the RTOW, i.e. 73500kgs.

The performance limited weight is a "maximum" of course but in terms of definitions it is not MTOW.

I have to join the ranks of those raising their eyebrows at the concept of on-the-day flexing of MTOWs. Could be it be that denti's company is, shall we say, exploiting a loophole ?

[de facto]

In general true, however for stuff like airway or landing fees the MTOW can be flexible again. We use around 8 to 10 different MTOWs and select the lowest usable for each flight. That MTOW is then the basis for all kind fees associated with that flight

Was the same in my previous airline.

[BOAC]

Just to complete the education for bh - RTOW can also be limited by landing weight.

de facto - how was the 'selective' MTOW notified to Eurocontrol and airports?

[de facto]

No idea.
Airline went bankrupt anyway.

[763 jock]

The best bit of bean counting I have seen is as follows:

Aircraft declared at 184 tonnes for an outbound flight (Banjul-fuel really proper expensive) so that maximum tanking could be utilised.

Inbound sector declared at the lower weight to avoid expensive nav and landing charges.

[vama]

The MTOW is your Structural max take off weight(real weight).
The RTOW (Regulated) is your Performance adjusted take off weight which must be below your runway/obstacle level off/climb limit weight.

The adjustments are qnh,bleeds OFf,EAI ON.....
On a long runway you could see that your RTOW limit is well above your MTOW,up to 82T for a 738.

I thought MTOW must never be exceeded irrespective ?

[vilas]

I thought MTOW must never be exceeded irrespective ?
True! So now RTOW will be restricted by MTOW.

[punkalouver]

Was the same in my previous airline.
Same here. It is known as the alternate MTOW and is applied at certain airports and and listed on the flight plan as a heads-up for flight crew awareness.

Then on the cockpit pre-flight check, one checks that a two-sided removable placard is displaying properly.

If using the alternate MTOW, that weight should be displayed. If using the normal MTOW, the blank side is displayed. If incorrectly displayed, let maintenance know and they will remove a couple of screws and flip it over.