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aesop081
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NINJA said:
Do a range comparaison for the Hornet between a HI-HI-HI mission profile and a LO-LO-LO ( or even HI-LO-HI) mission profile and you will see what low altitude does to a jet.
Do a range comparaison for the Hornet between a HI-HI-HI mission profile and a LO-LO-LO ( or even HI-LO-HI) mission profile and you will see what low altitude does to a jet.
B
belka
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CDN Aviator said:
Yes, I'm aware that the Hornet will be more efficient at higher altitudes. I think I had efficiency and power output confused here. Then I agree that at lower altitudes a turbofan consumes more fuel than a turboprop.
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I have 2 questions regarding high bypass turbofans at low altitude if anybody could help me out I'd appreciate it,
1. My understanding is that jet engines are more efficient at altitude due to the out side air being colder than it may be at sea level. If this is correct then would the cold air in the arctic have the same affect on fuel consumption and engine performance at lower altitudes?
2. How does corrosion from salt water mist affect engine life?
1. My understanding is that jet engines are more efficient at altitude due to the out side air being colder than it may be at sea level. If this is correct then would the cold air in the arctic have the same affect on fuel consumption and engine performance at lower altitudes?
2. How does corrosion from salt water mist affect engine life?
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aesop081
Guest
thunderchild said:
You are not grasping the concept of use of the P-8. The days of spending 10 hours on station below 1000 feet are over.
We have agressive corosion control programs to minimize this.
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My mistake, I understood that most ASW was between 1000-2000 feet. Thanks.
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aesop081
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thunderchild said:
:
As of right now, with a P-3 type airframe, yes ( relatively speaking). The P-8 will be a departure from that.
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Thunderchild, as to your first question, no, turbofans are not more efficient at altitude due to the cold air. The gain in efficiency is because they are operating closer to their design point.
To simplify somewhat, these engines are at their most efficient when operating at their highest combustion temperatures and core turbine speeds. They are so powerful, that the only time they can approach this without overspeeding the airframe is in a climb or, in the thin air at high altitude. You can think of a turbine as an unturbocharged reciprocating engine. The lower the mass of air it takes in, the less power it can produce. The air at 40,000 ft is about one fifth as dense as that at sea level. For example, the max power output of the CFM56-7b26K at sea level is 26,000 lbs of thrust, and at that, it is limited by the allowable power in the fan. As the engine climbs, the exhaust gas temperature will rise and at some point the temp reaches it's max allowable value and becomes the limiting factor instead of the fan. As the engine climbs further, power drops off. At the 737's max operating altitude of 41,000 ft, it's engines are making maybe a quarter of what they did at take-off but, they still have enough power to overspeed the airframe in level flight.
The other side to the thin air is the reduced resistance it poses to the airplane's passage. This resistance, called drag, is proportional to the density of the air and is therefore greatly reduced at altitude. This is all pretty basic and simplified, there are several more factors at play here but, simply, no, cold arctic air would offer no benefit to fuel consumption.
On point 2, it is common practice for all 737 operators to perform compressor washes on a regular basis. It would be unusual for the airforce not to perform this maintenance regardless of salt water ingestion, further, the equipment for this would be an off the shelf purchase.
I can't comment on any of the operational procedures Canadian Aviator has already addressed.
Cheers
Steve
To simplify somewhat, these engines are at their most efficient when operating at their highest combustion temperatures and core turbine speeds. They are so powerful, that the only time they can approach this without overspeeding the airframe is in a climb or, in the thin air at high altitude. You can think of a turbine as an unturbocharged reciprocating engine. The lower the mass of air it takes in, the less power it can produce. The air at 40,000 ft is about one fifth as dense as that at sea level. For example, the max power output of the CFM56-7b26K at sea level is 26,000 lbs of thrust, and at that, it is limited by the allowable power in the fan. As the engine climbs, the exhaust gas temperature will rise and at some point the temp reaches it's max allowable value and becomes the limiting factor instead of the fan. As the engine climbs further, power drops off. At the 737's max operating altitude of 41,000 ft, it's engines are making maybe a quarter of what they did at take-off but, they still have enough power to overspeed the airframe in level flight.
The other side to the thin air is the reduced resistance it poses to the airplane's passage. This resistance, called drag, is proportional to the density of the air and is therefore greatly reduced at altitude. This is all pretty basic and simplified, there are several more factors at play here but, simply, no, cold arctic air would offer no benefit to fuel consumption.
On point 2, it is common practice for all 737 operators to perform compressor washes on a regular basis. It would be unusual for the airforce not to perform this maintenance regardless of salt water ingestion, further, the equipment for this would be an off the shelf purchase.
I can't comment on any of the operational procedures Canadian Aviator has already addressed.
Cheers
Steve
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Thanks SteveB, I hadn't taken air density into account.
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aesop081
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thunderchild said:
....amongst other things you havent taken into account because you simply just dont know.
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The CF can hope:
Navy to begin Initial Production of P-8A
http://www.navair.navy.mil/NewsReleases/index.cfm?fuseaction=home.view&id=4481
NAVAL AIR SYSTEMS COMMAND, PATUXENT RIVER, Md. - The U.S. Navy announced today the award of a $1.6 billion contract to Boeing for P-8A Poseidon aircraft Low-Rate Initial Production (LRIP) of six aircraft.
This first LRIP contract also includes spares, logistics and training devices. Production of the first LRIP aircraft will begin this summer at Boeing’s Renton, Wash. facility.
“In 2004, the U.S. Navy and the Boeing Company made a commitment to deliver the next generation maritime patrol and reconnaissance aircraft to support a 2013 Initial Operational Capability (IOC),” said Capt. Mike Moran, PMA 290 Program Manager. “This contract and these aircraft keep that commitment on track.”
Three of the six flight test aircraft, built as part of the System Development and Demonstration contract awarded to Boeing in 2004, are in various stages of testing at Naval Air Station Patuxent River, Md. The Integrated Test Team has conducted sonobuoy releases and counter measures deployments.
Recently, one of two static test planes completed full scale testing on the P-8A airframe. The first static test aircraft underwent 154 different tests with no failure of the primary structure. The second aircraft will begin fatigue testing this year.
The U.S. Navy plans to purchase 117 production P-8A aircraft to replace its P-3 Fleet. IOC is planned for 2013 at NAS Jacksonville, Fla.
Plus:
P-8i: India’s Navy Picks Its Future High-End Maritime Patrol Aircraft
http://www.defenseindustrydaily.com/indias-navy-holding-maritime-patrol-aircraft-competition-updated-01991/
Mark
Ottawa
Navy to begin Initial Production of P-8A
http://www.navair.navy.mil/NewsReleases/index.cfm?fuseaction=home.view&id=4481
NAVAL AIR SYSTEMS COMMAND, PATUXENT RIVER, Md. - The U.S. Navy announced today the award of a $1.6 billion contract to Boeing for P-8A Poseidon aircraft Low-Rate Initial Production (LRIP) of six aircraft.
This first LRIP contract also includes spares, logistics and training devices. Production of the first LRIP aircraft will begin this summer at Boeing’s Renton, Wash. facility.
“In 2004, the U.S. Navy and the Boeing Company made a commitment to deliver the next generation maritime patrol and reconnaissance aircraft to support a 2013 Initial Operational Capability (IOC),” said Capt. Mike Moran, PMA 290 Program Manager. “This contract and these aircraft keep that commitment on track.”
Three of the six flight test aircraft, built as part of the System Development and Demonstration contract awarded to Boeing in 2004, are in various stages of testing at Naval Air Station Patuxent River, Md. The Integrated Test Team has conducted sonobuoy releases and counter measures deployments.
Recently, one of two static test planes completed full scale testing on the P-8A airframe. The first static test aircraft underwent 154 different tests with no failure of the primary structure. The second aircraft will begin fatigue testing this year.
The U.S. Navy plans to purchase 117 production P-8A aircraft to replace its P-3 Fleet. IOC is planned for 2013 at NAS Jacksonville, Fla.
Plus:
P-8i: India’s Navy Picks Its Future High-End Maritime Patrol Aircraft
http://www.defenseindustrydaily.com/indias-navy-holding-maritime-patrol-aircraft-competition-updated-01991/
Mark
Ottawa
Oldgateboatdriver
Army.ca Veteran
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1.6 B$ for six. Wow! They look like a steal compared to a F-35
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Full rate production will be cheaper.Oldgateboatdriver said:1.6 B$ for six. Wow! They look like a steal compared to a F-35
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MarkOttawa said:
I hope you kick up a fuss if we sole-source these like you're doing with the F-35. I'm sure the P8 is a superior platform to anything out there currently, but we would want to waste a lot of money to double check that fact, right?
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PuckChaser: I had no objection to sole-sourcing the Jerc or the C-17. No conceivable competitors. The P-8 may be in the same situation, but there is a long time before a formal Aurora replacement process gets going and we'll need to see what the situation is then and what is available (UAVS, satellite, civilian patrol, other aircraft).
It is thought-provoking that the RAF has got entirely out of the maritime patrol business:
http://forums.milnet.ca/forums/threads/81956/post-993951.html#msg993951
Also interesting that the Air Force is touting the F-35 as being useful for sneaking up on and identifying ships.
Mark
Ottawa
It is thought-provoking that the RAF has got entirely out of the maritime patrol business:
http://forums.milnet.ca/forums/threads/81956/post-993951.html#msg993951
Also interesting that the Air Force is touting the F-35 as being useful for sneaking up on and identifying ships.
Mark
Ottawa
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If we pick the P8 without competition then it will be the exact same scenario as the F-35, the US ran a competition and we picked the winner. Except with the P-8, we're not multi-millions into the project with numerous contracts for our aerospace industry in the balance.
Hold a competition. Only Boeing will show up because they have the only aircraft that can close to meeting a realistic spec doc.
We could do the same for the F35. Only LM would show up. There are no other available aircraft that could meet the stealth profiles that we would put in a spec.
A waste of time & money. Then Iggy & Layton & the fools at the Rideau Centre would be complaining about wasting money.
Anyone catch Staples on QP today? He went on and on about how the F35 was "a bomb truck"
Dumber than a bag of hammers that one.
We could do the same for the F35. Only LM would show up. There are no other available aircraft that could meet the stealth profiles that we would put in a spec.
A waste of time & money. Then Iggy & Layton & the fools at the Rideau Centre would be complaining about wasting money.
Anyone catch Staples on QP today? He went on and on about how the F35 was "a bomb truck"
Dumber than a bag of hammers that one.
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Mark have you ever tracked low flying fast moving targets at sea?
A
aesop081
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The P-8 was deemed too expensive. Buying the quantity needed was not possible given the funding envelope available. CP-140 AIMP will extend the aircraft until 2025-ish and the hope is that there will be alternatives to the P-8 by then.
I'm not sure how many more times i can explain to YOU that no civillian patrol scheme can replace the CP-140........none.
MarkOttawa said:
I'm not sure how many more times i can explain to YOU that no civillian patrol scheme can replace the CP-140........none.
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CDN Aviator said:
Q-400 with hard points? Is it the ability to drop weapons that makes this not feasible? PAL flies B200's with pretty jammy EO/IR/EW gear. Anyone can drop a torp - you just need the appropriate laws to back you up.
Every single trade in the CF can be privatized.
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