CaptainKramer
Topic Author
Posts: 256
Joined: Thu Feb 09, 2012 8:12 pm

OEM's And Weight Guarantee's On New Aircraft

Mon May 07, 2012 3:08 pm

When an OEM such as, Airbus, Boeing, Bombardier or Embraer design a clean sheet aircraft, once they have signed the contract with the airlines to build the new aircraft to a certain specification, two critical area's need to be met, amongst others, weight guarantee's which ulitmately determine whether you can met your range guarantee's.

My questions are as follows. Please do not feel obliged to answer them all.

Before the days of outsourcing ,if say for instance Boeing designed a part, then awarded a U.S.company to manufacter it and it came in overweight, who would take the penaly hit? Boeing for failing to design it in a way that it could be manufactered to weigh less, or is the onus fully on the supplier who failed to keep the weight out?

How has outsourcing oversea's to non U.S. maufacturers with the onus of both designing and building the part, complicated these matters of penalties regarding weight or has it simplified things.

In the days before outsourcing how did OEM's orchestrate or design what weight goes where on an aircraft, do they use previous builds of previous generations of aircraft as a yard stick? Has the transition from aluminium to CFRP meant that the rule book was thrown out the door. Will future bulid CFRP's be easier with experience gained on say B787 or A350XWB or are there gotchas still to be had?

When all the parts come in for final assembly are they weighed individually to guage if the final assembled aircraft will be overweight, how does a Company like Airbus or Boeing have an idea ahead of the actual build that the aircraft will be overweight while still in the design phase?

When it comes to the final weigh in, I remember watching a program on the making of the B777. They used 3 scales with each landing gear resting on a respective scale and they would add up the 3 totals. During this weighing phase is the aircraft fueled or unfueled, hydraulic fluids added or not, cabin or galley furnishings added or not.

If RR engine weighs more or less than say P&W or GE is this final weight subtracted from the final weight of the aircraft that was guaranteed by Boeing or Airbus or do they guarantee on OEW or ZFW.

If the aircraft is overweight, how do they caculate the penalty? How is this passed on down the line so to speak from OEM to supplier? Is the penalty paid over years, can any real world examples be given e.g. A340-600. With upgrades or redesigns the weight is taken out progressively, how is this factored in regarding penalties?

I know there are alot of questions that cannot be answered in depth, but any responses will be fully appreciated.

Thanks Frank.
 
prebennorholm
Posts: 6409
Joined: Tue Mar 21, 2000 6:25 am

RE: OEM's And Weight Guarantee's On New Aircraft

Tue May 08, 2012 2:38 am

The answer to all your questions will be pure guesswork without reading all the small print in the airline purchase contracts and OEM sourcing contracts.

Quoting CaptainKramer (Thread starter):
Is the penalty paid over years, can any real world examples be given e.g. A340-600.

The A346 is a "bad" example since it is one of the very few 21st century designs which actually met contract weight.

The A346 is considered heavy compared to the competition, mainly B777. But that's not overweight. Actual empty weight minus empty weight in purchase contract = overweight.

It doesn't mean that Airbus hasn't got weight complaints. A few operators, who opted for heavy premium class furniture up front, and lightweight Y class seats with reasonably generous seat pitch in the back, were surprised that it easily became nose heavy. Meaning that it was often difficult to fully utilize the volume of the forward cargo space. To fully utilize its cargo volume and weight capability somewhat denser cargo has to go in the back compared to the front cargo bay. But that is a balance problem, not an overweight problem.

Airbus dismissed the complaints saying that balancing cargo and balancing customized cabin furniture are equally important issues for balancing the plane for optimal performance.

None complained about the plane being tail heavy, so maybe Airbus regrets that they didn't put the wing one or two feet further forward on the fuselage? We will most likely never know about that.
Always keep your number of landings equal to your number of take-offs
 
CaptainKramer
Topic Author
Posts: 256
Joined: Thu Feb 09, 2012 8:12 pm

RE: OEM's And Weight Guarantee's On New Aircraft

Tue May 08, 2012 8:03 am

Thanks prebennorholm for your contribution anyway.
 
tdscanuck
Posts: 8572
Joined: Wed Jan 11, 2006 7:25 am

RE: OEM's And Weight Guarantee's On New Aircraft

Tue May 08, 2012 9:32 am

Quoting CaptainKramer (Thread starter):
weight guarantee's which ulitmately determine whether you can met your range guarantee's.

Weight guarantees, by themselves, don't define the range. Airlines' main care is the payload range curve, which rests primarily on OEW, ZFW, MTOW, aerodynamics, and engine efficiency. You can make up for shortfall in any one of those by adjusting some of the others (if you can). This is why you often see MTOW creep in new programs as a way of recovering range in the face of OEW creep.

Quoting CaptainKramer (Thread starter):
Before the days of outsourcing ,if say for instance Boeing designed a part, then awarded a U.S.company to manufacter it and it came in overweight, who would take the penaly hit?

The OEM. That's who the customer contracted the penalty with. The OEM may or may not have guarantees with their suppliers but that's an entirely separate issue. Until recently, most suppliers were build-to-print or build-to-spec. Build-to-print has no exposure since they're just building what they're told. Build-to-spec may or may not, depending on the spec and contract.

Quoting CaptainKramer (Thread starter):
How has outsourcing oversea's to non U.S. maufacturers with the onus of both designing and building the part, complicated these matters of penalties regarding weight or has it simplified things.

With respect to weight, I don't think anything has changed.

Quoting CaptainKramer (Thread starter):
In the days before outsourcing how did OEM's orchestrate or design what weight goes where on an aircraft, do they use previous builds of previous generations of aircraft as a yard stick?

Yes. Product development guys have pretty good heuristics and historical data to gauge approximate weight.

Quoting CaptainKramer (Thread starter):
Has the transition from aluminium to CFRP meant that the rule book was thrown out the door.

Density of CFRP is relatively constant, just like aluminum, so weight calculation is still pretty straight forward.

Quoting CaptainKramer (Thread starter):
Will future bulid CFRP's be easier with experience gained on say B787 or A350XWB or are there gotchas still to be had?

Yes.

Quoting CaptainKramer (Thread starter):
When all the parts come in for final assembly are they weighed individually to guage if the final assembled aircraft will be overweight,

No. Maybe pre-CAD but not anymore.

Quoting CaptainKramer (Thread starter):
how does a Company like Airbus or Boeing have an idea ahead of the actual build that the aircraft will be overweight while still in the design phase?

In a full digital mockup (777 and onwards at Boeing), CAD programs know the geometry and density of all parts so they know weight.

Quoting CaptainKramer (Thread starter):
When it comes to the final weigh in, I remember watching a program on the making of the B777. They used 3 scales with each landing gear resting on a respective scale and they would add up the 3 totals. During this weighing phase is the aircraft fueled or unfueled, hydraulic fluids added or not, cabin or galley furnishings added or not.

Depends on when you're weighing. I believe the normal production weight is post-paint, post-interior, pre-fuel so it would basically be OEW minus customer items to be supplied. However, whenever you weight you are just setting a baseline that you then document all deviations to. So, if you weighed before you had galley furnishings, you'd just amend the weight with the weight of the galley furnishings when you installed them.

Quoting CaptainKramer (Thread starter):
If RR engine weighs more or less than say P&W or GE is this final weight subtracted from the final weight of the aircraft that was guaranteed by Boeing or Airbus or do they guarantee on OEW or ZFW.

There will be a different OEW and ZFW for each engine if there are meaningful differences in engine weight.

Quoting CaptainKramer (Thread starter):
If the aircraft is overweight, how do they caculate the penalty? How is this passed on down the line so to speak from OEM to supplier? Is the penalty paid over years, can any real world examples be given e.g. A340-600. With upgrades or redesigns the weight is taken out progressively, how is this factored in regarding penalties?

It all depends on the contract.

Tom.
 
CaptainKramer
Topic Author
Posts: 256
Joined: Thu Feb 09, 2012 8:12 pm

RE: OEM's And Weight Guarantee's On New Aircraft

Tue May 08, 2012 8:55 pm

Thanks tdscanuck,

Building aircraft can be complicated at the best of times just from an engineering standpoint, but the mind boggles sometimes when all the issues that arise are factored in, especially the contractual side, including the discussion, design, build, and then the redesign, rebuild stages that may follow.

Who is online

Users browsing this forum: No registered users and 10 guests