Northrop B-2 Spirit - First Cockpit Video

[tom slick]

Originally Posted by JetStar
Originally Posted by tom slick
The B-2 (and U-2) uses a variant of an F-16, F-14, and F-15 (export) engine, the GE F118. It is very robust. If I remember correctly it was about 6000 hrs between rebuilds in F-16 service.


B-1; F101
B-2: F118
U-2S: F29
F-16: F110-100 and -129
F-15 F110-132 (export)
F-14 F110-400

All based on the CFM56 core, with incremental improvements


True, the F110/F118 series are based on the F101, which use a core based on the CFM56. The F101 definitely a different engine than the F110/F118 series though.

 

[Astro14]

Originally Posted by pitzel
Originally Posted by Astro14

If you're flying formation, thrust changes are made about every second. It's the nature of formation flying.


Minor changes. And formation flying is very uncommon and mostly confined to military aircraft. Whereas on the B-2, the settings probably would be changing nearly all the time, every minute the airframe is in flight.

Quote

If a gas turbine can't handle that, it shouldn't be in a military airplane. Period.


The turbines can "handle" that (obviously the B-2 is flying), but at what price in terms of reliability? Would they even get 1000 flight hours out of an engine that's being cycled like that all the time? Can't imagine they're easy engines to change either, unlike the B-52's... And just how nasty is a plane that relies on the engines for stability control to fly in an engine out situation?


Why are you arguing?

Formation flying, and rapid, frequent thrust changes, are part of military service.

OK?

That's why the design specifications include the ability to handle that.

If the military flew like you wanted, minimal thrust changes. they would not be able to accomplish the mission. Can't in flight refuel. Can't fly combat maneuvers. Can't fly carrier landings. Can't do anything except straight and level airliner flying.

The in-service experience of the F-110 (all variants) demonstrates that they CAN handle that kind of use and meet reliability goals.

We got way more than 1,000 hours out of an F-110 that was put through constant power changes, throttle slams from idle to AB and AB to idle. The engines are built for that.

At what cost in reliability?

Don't really care.

I bet we could get 60,000 hours out of an F/A-18 airframe, instead of the 6,000 design life, if it never pulled G, never carried bombs on the wing, and never landed on a carrier.

But what good would it be?

Besides, even in cruise flight, turbine engines on airliners are making constant power changes.

How much turbine flight time do you have, on which you're predicating your position?

 

[CT8]

"I bet we could get 60,000 hours out of an F/A-18 airframe, instead of the 6,000 design life, if it never pulled G, never carried bombs on the wing, and never landed on a carrier".
Operate the F/A 18 like an airliner?

 

[Astro14]

Exactly.

Point is: military flying is hard on equipment.

It has to be, so that the mission can be accomplished.

 

[53' Stude]

Originally Posted by Astro14
Exactly.

Point is: military flying is hard on equipment.

It has to be, so that the mission can be accomplished.


Astro14: my stepdad read what "pitzel" wrote and just shook his head. Good reason I have him on "ignore" as he knows nothing about aircraft

 

[CT8]

I having watched this video countless times, I can't help but say that our military pilots do have that something extra. Here we go And I do apologize in advance to all those that have already watched this video and those that may be offended by the pilot spirit.

 

[2strokeNorthstar]

Show us the Electrogravitic propulsion switch!

 

[CT8]

Originally Posted by tom slick
Originally Posted by JetStar
Originally Posted by tom slick
The B-2 (and U-2) uses a variant of an F-16, F-14, and F-15 (export) engine, the GE F118. It is very robust. If I remember correctly it was about 6000 hrs between rebuilds in F-16 service.


B-1; F101
B-2: F118
U-2S: F29
F-16: F110-100 and -129
F-15 F110-132 (export)
F-14 F110-400

All based on the CFM56 core, with incremental improvements


True, the F110/F118 series are based on the F101, which use a core based on the CFM56. The F101 definitely a different engine than the F110/F118 series though.
About 750 8 hour days and tbo doesn't mean at the hours usually engine fails, if I an correct with the statement?

 

[pitzel]

Originally Posted by 53' Stude
Originally Posted by Astro14
Exactly.

Point is: military flying is hard on equipment.

It has to be, so that the mission can be accomplished.


Astro14: my stepdad read what "pitzel" wrote and just shook his head. Good reason I have him on "ignore" as he knows nothing about aircraft


That's unfortunate. Because I merely asked how bad for an engine it would be to always be changing the thrust settings as the B-2 obviously does as part of its stability control system. Gas turbines, at least in industry, do not like constant changes to their fuel flow/thrust as such stresses internal components beyond just that implied of steady state operation. Obviously in an aircraft, some thrust changes are unavoidable, but the extreme frequency with which the B-2 engines are changing their thrust settings as part of their stability control *may* induce reliability-related issues.

Its worth noting that engines on the fighters (ie: that use the F101 engine) are not changing their thrust every few seconds. Nor are engines attached to airliners. Reliability of an engine impacts the mission-capable rate of an aircraft and ultimately the cost of the system to the warfighter/taxpayer. Obviously such was one of the design compromises made to achieve the B-2's low-radar-observability characteristics. My question was at what cost to reliability?

Quote
If the military flew like you wanted, minimal thrust changes. they would not be able to accomplish the mission. Can't in flight refuel. Can't fly combat maneuvers. Can't fly carrier landings. Can't do anything except straight and level airliner flying.


Combat manouevres, carrier landings, in-flight refueling, that's a small fraction of the overall operational time on those engines in those applications. Maybe 2-5% of flight hours. The rest is spent in straight and level flight which involves minimal (or extremely gradual) thrust changes. In the B-2, the engines are changing thrust, and quite significantly, literally *all the time*.

So what I'm asking is whether this substantially reduces the TBO or introduces unique failure modes that are not experienced on engines that spend 95% of their operational life operating with minimal to no thrust changes. If the TBO or "on-wing" time is classified on the B-2, I can accept that, but I just can't buy the argument that changing thrust settings nearly 100% of the time as part of the stability control system doesn't have a negative impact on certain engine components.

Quote
How much turbine flight time do you have, on which you're predicating your position?


Flight time would be irrelevant as the question is one of maintenance. A pilot is no more of a turbine maintenance expert than a car driver or even quickie lube tech is an expert on motor oil or ICE maintenance.

 

[tom slick]

The C-130's T-56/54H60 engine/propeller uses a Syncrophaser system to control vibration (harmonics) that constantly varies engine rpm and propeller pitch to keep its propellers in sync.

 

[pitzel]

Originally Posted by tom slick
The C-130's T-56/54H60 engine/propeller uses a Syncrophaser system to control vibration (harmonics) that constantly varies engine rpm and propeller pitch to keep its propellers in sync.


But how much of a difference in actual power output are we talking about here? A minor tweak to the fuel flow to get rid of resonant modes that may be excited by non-synchronized propellers is nothing compared to an engine cycling between (for example) 70% and 90% power hundreds of times an hour for every flight hour as part of a stability or maneuvering control system.

 

[tom slick]

Here's some interesting reading about the B-2 development program

https://www.northropgrumman.com/Cap...geDocuments/B-2-Spirit-of-Innovation.pdf

 

[53' Stude]

Originally Posted by pitzel
Originally Posted by 53' Stude
Originally Posted by Astro14
Exactly.

Point is: military flying is hard on equipment.

It has to be, so that the mission can be accomplished.


Astro14: my stepdad read what "pitzel" wrote and just shook his head. Good reason I have him on "ignore" as he knows nothing about aircraft


That's unfortunate. Because I merely asked how bad for an engine it would be to always be changing the thrust settings as the B-2 obviously does as part of its stability control system. Gas turbines, at least in industry, do not like constant changes to their fuel flow/thrust as such stresses internal components beyond just that implied of steady state operation. Obviously in an aircraft, some thrust changes are unavoidable, but the extreme frequency with which the B-2 engines are changing their thrust settings as part of their stability control *may* induce reliability-related issues.

Its worth noting that engines on the fighters (ie: that use the F101 engine) are not changing their thrust every few seconds. Nor are engines attached to airliners. Reliability of an engine impacts the mission-capable rate of an aircraft and ultimately the cost of the system to the warfighter/taxpayer. Obviously such was one of the design compromises made to achieve the B-2's low-radar-observability characteristics. My question was at what cost to reliability?

Quote
If the military flew like you wanted, minimal thrust changes. they would not be able to accomplish the mission. Can't in flight refuel. Can't fly combat maneuvers. Can't fly carrier landings. Can't do anything except straight and level airliner flying.


Combat manouevres, carrier landings, in-flight refueling, that's a small fraction of the overall operational time on those engines in those applications. Maybe 2-5% of flight hours. The rest is spent in straight and level flight which involves minimal (or extremely gradual) thrust changes. In the B-2, the engines are changing thrust, and quite significantly, literally *all the time*.

So what I'm asking is whether this substantially reduces the TBO or introduces unique failure modes that are not experienced on engines that spend 95% of their operational life operating with minimal to no thrust changes. If the TBO or "on-wing" time is classified on the B-2, I can accept that, but I just can't buy the argument that changing thrust settings nearly 100% of the time as part of the stability control system doesn't have a negative impact on certain engine components.

Quote
How much turbine flight time do you have, on which you're predicating your position?


Flight time would be irrelevant as the question is one of maintenance. A pilot is no more of a turbine maintenance expert than a car driver or even quickie lube tech is an expert on motor oil or ICE maintenance.



Thanks for the insult Pitzel. Mods notified also. I'm not a quickie lube tech btw so thanks for that snarky jab

.

 

[pitzel]

Originally Posted by 53' Stude


Thanks for the insult Pitzel. Mods notified also. I'm not a quickie lube tech btw so thanks for that snarky jab

.


Insult? What insult? Just trying to understand what's going on here since it was implied that I might be out of line for asking maintenance and reliability questions. Any time you have a high degree of cycling on any component in any system, whether it be an aircraft, automotive or industrial engine, etc., you're going to have potential maintenance and reliability concerns relative to machinery that is run continuously in steady-state operation. I know in the gas turbine world, the GE CF6-80 (aircraft engine) is hard pressed to spend 20,000 hours before requiring major maintenance, while the stationary gas turbine version of the same motor (GE LM6000) is good for triple that.

 

[Mr Nice]

Not trying to change the subject...

AgentJayZ on YouTube rebuilds jet engines and gas turbines and does a great job of going in depth about turbine failure / maintenance / problems... , etc...