[A350XWB]

Originally Posted by V.Narayan

Larger aircraft such as the 747, 380, 777, have an extra fitment for a pod under one wing to be fitted with a spare/damaged engine that can then be flown to the MRO centre where ever in the world.

AFAIK, the A380 or 777 do not have the capability to ferry an additional engine under the wing. This capability was added to the 747, as at the time it entered service, large transports were a rarity and also the reliability of turbofans were nowhere near the current levels.

[Sutripta]

Experts - your thoughts please.
https://www.bloombergquint.com/amp/b...bus-groundings

Regards
Sutripta

[Aditya_Bhp]

Originally Posted by Sutripta

Experts - your thoughts please.

There have been no issues with Indigo's Airbus A320ceos. And its not just an 'India' only issue. Every single operator using Airbus A320neos and A220s with P&W GTF engines have face some or the other issue with the engine. Be it engine shutdowns, vibrations, gearbox issues, the engine is excellent value but is not at all perfect. If this engine cannot survive in the world's largest neo market and with the world's largest neo customer, then it doesn't deserve to be an option. Airbus should remove it as an option, and instead use CFM engines, they may be slightly less advanced but they have been reliable.

I do not think blaming Indigo for engine failures by operating them at full thrust is justified as they should be able to handle all sorts of extreme conditions without failing.

[V.Narayan]

Originally Posted by Sutripta

Experts - your thoughts please.
https://www.bloombergquint.com/amp/b...bus-groundings

Regards
Sutripta

As Aditya_bhp states this sounds like so much of journalistic cockamamie to me fed by rival airlines. An engine suffering high failure rates because of being revved up for 10 to 12 minutes 6 to 8 times a day sounds too outlandish to believe. That is something engines are designed for. However most airliners do not climb at full thrust or even 90% thrust. Military fighters on the other hand almost always take off and climb at full thrust. P&W have taken longer than warranted to fix their issues.

[Sutripta]

First question is whether there is actually a (statistics supported) difference in the problem rate of Go and Indigo. In fact an analysis of all operators is needed. Not for fingerpointing but for insights and understanding. This is not to say the GTFs are reliable - it is not. But if in the meantime changes in operating procedures can reduce problems ..

What are DGCAs instructions to GoAir? Same as that for Indigo?

Regards
Sutripta

[Motard_Blr]

This is what Boeing has to say about engine thrust during takeoff:

From a fuel consumption perspective, a full-thrust takeoff and a full-thrust climb profile offer the most fuel economy for an unrestricted climb. However, from an airline’s cost perspective, this must be balanced with engine degradation and time between overhauls, as well as guidance from the engine manufacturer. The airline’s engineering department must perform the analysis and provide direction to flight crews to minimize overall cost of operation when using takeoff derates or assumed tempera*ture takeoffs and climbs.

Source: https://www.boeing.com/commercial/ae...icle_05_3.html

This supports what the DGCA has said.

Boeing makes no specific mention of geared turbo fan engines, so it can be assumed that this statement covers all types of aero engines.

The IndiGo strategy is to keep a young fleet to avoid expensive repairs and maintenance as the planes age. They are more concerned about fuel consumption than with engine wear as that would NORMALLY not be an issue if the plane is sold after only 5 or 6 years. Fuel is the biggest expense for Indian airline companies.

[Sutripta]

https://www.livemint.com/companies/n...293267984.html

Regards
Sutripta

[Jeroen]

What is is that actually breaks and what is the correlation to full thrust settings for 8-12 minutes?

How was the 93% determined? I wonder how much difference there is in the various temperatures, pressures and RPM between 93 and 100% thrust?

If I read this correctly it is not the engine manufacturer that has come up with this?

What is the formal P&W stand? Bit of a finicky engine if you can not run it all full thrust now and then.

Will it have any operational consequences for the operator? Any fields where they have to limit weight as they will need to derate?

Jeroen

[V.Narayan]

I do not know the figures for Indigo's PW engines and commercial pilots can opine better but generally to get thrust up from 80% to 100% requires a completely disproportionately high increase in RPM. As an example turbojets of the 1960s and 1970s vintage developed 80% of non-afterburning thrust at just 33% of the RPM. I suspect figures for a modern high by-pass turbofan should also broadly be in the same direction. But as I said the commercial pilots or maintenance engineers will know better.

[Sutripta]

^^^
Will this hold true where a significant portion of the thrust comes from the (geared) fan?

Regards
Sutripta

[Jeroen]

I would expect RPM and thrust to be pretty linear especially on high by pass engines. Fuel versus RPM/thrust is very different of course.

I will need to look it up when I get back home later this week. My memory is not what it used to be anymore.

Jeroen

[V.Narayan]

Originally Posted by Sutripta

^^^
Will this hold true where a significant portion of the thrust comes from the (geared) fan?

Regards
Sutripta

Your question is bang on. For the big fan at front it seems it should be proportional. But I don't know.

[Sutripta]

For centrifugal, pressure follows square of rpm, volume proportional to rpm. Axial I believe has more complicated relationship.

Originally Posted by Jeroen

What is is that actually breaks

I believe the low pressure turbine blades and seals fail. Amongst other problems. There is also a problem with vibration. Don't know if it is a result of other problems, or independent.

Regards
Sutripta

[Sutripta]

Originally Posted by Sutripta

What are DGCAs instructions to GoAir? Same as that for Indigo?

A bit of digging shows that both Go and Indigo were given the same notice.

Regards
Sutripta

[Sutripta]

Carroll Lane takes over PWs commercial engines business. (Feminists note - he, not she!)

Previous head Christopher Calio promoted, not ousted.

Regards
Sutripta