Warbird Information Exchange

http://www.centennialofflight.gov/essay ... /Tran6.htm

He says the unusual aspects is how fast all the airlines adopted the jets?
I would like to know how that can be. Since they at the time consummed way more fuel than a recip, and weren't all that reliable either.
I'd like to know the real facts. Subsidies?

Speed, over weather performance, and reliability/maintenance issues. Beyond that, the marketing folks really sold the jets, so pretty soon passengers were using jet vs recip as a decision maker in picking their airline/route.

On a cost basis, jet fuel probably wasn't that much more expensive than avgas on a passenger mile basis...

No subsidies that I'm aware of. It's all about productivity and the economics were substaniial once jet engine technology had matured to a point where it was saleable to the airlines.

1: Speed. A jet can carry more passengers more miles in a day than a recip, so there each jet can provide substantially more seat miles per hour. A jet can easily do 3 transcontinental flights in a day, I don't think a Connie could even do two. This is the single biggest reason the airlines went for the jets.

2: Even the early passenger jets were significantly more reliable than the recips.

3: Lower maintainence costs. A jet engine requires far fewer maintainence hours per flight hour than a recip. Fewer hours in the hangar= more productivity.

Remember that fuel was amazingly cheap at the time. Also the fact that the airlines were regulated made it easier for them to pass costs like fuel on to the passenger.

Howard Hughes ordered Connies for TWA when everyone else was buying jets. I have seen it argued that TWA never really bounced back from that decision.

Steve

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Steve
www.eaglesmereairmuseum.org
www.net2nite.com

1 speed. Well when a P51 could pretty much fly along side a jet liner, and the talk of slowing the jets down to conserve fuel, I think speed is a non issue.

2 Reliablilty, we were told they were more reliable, I know that turbines suffered from lots of stress cracks etc. Maybe the engine changes were just alot faster with jets.

3 Normal maintenance maybe, but at overhaul time the recips are still cheaper. How much to overhaul an engine from a 737, 777 or airbus? is it 3 or 4 million?

Speed IS a huge issue. A P-51 cruises at 250-300 mph. Jets cruise at twice that. Even better, a 600 mph jet bucking a 100 mph headwind still gives a 500 mph ground speed. The slower an airplane is, the more it is impacted by headwinds.

From a reliability perspective, everything breaks, but even early commercial turbines had MTBF's that were far higher than recips. Most big radials, transport Merlins, etc. required plenty of plug changing, cylinder changing, etc. And that was at the peak of the technology and with brand new engines. Today's turbines can go tens of thousands of hours, and they fly twice as far per hour of run time.

I'm not sure you can reasonably compare the overhaul cost of a turbine that can deliver 50,000 lbs of thrust or more for 10 or 20 thousand hours against a recip which produces a small fraction of the power and has a thousand hour TBO.

The speed is the big issue. Speed and payload= producivity. Carrying twice the payload at almost twice the speed was what sold the airlines.

Maintainence costs and reliability were much better, also. Even if they were the same on a per hour basis (they were not) remember that the jet is at least twice as productive as the recip

Even if the p 51 could keep up with the a 707 (it can't,) I'm not so sure about flying 200 P-51s across the country vs 1 707. That's without considering meals, movies and bathrooms. (or what all those p-51s would do the value of the existing fleet.)

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Steve
www.eaglesmereairmuseum.org
www.net2nite.com

Well again we are talking pretty much 1940's and 1950's aerodynamics and engineering.

If the old blimp nosed 377 had a max of 375 MPH and cruised at well the same as the P51, all the time burning way less fuel than you could even dream of in a Jet plane. Imagine what could be accomplished nowadays. The R-3350-TC18's were doing somewhere in the .32 BSFC area and how long ago was that.
Gosh I remember wasn't too long that there was talk of making a Boeing plane with a propeller, to improve the effciency of the engines.

As far as maintenance most of the average public is out of the loop as far as how long the Jet engines really last, yeah a few may go high time. But just like the recip stuff that fifi has I bet a great many jets blow in the first few hundred hours, that is not something that is going to be allowed to hit the news stands, I think some of the bird strikes could be an excuss for some other failure. There is alot of heat cycling in jet engines, and top that off with high frequency vibrations, things can happen. I used to make jet engine parts, and saw some that didn't last very long. And they are not cheap items to make, the parts are made of very expensive exotic materials to withstand the heat. Gosh I remember a few parts that would easily fit in a bread box that were to cost $20,000 a copy. The word Jet is expensive, in parts and fuel and maintenance/overhaul.

http://www.boeing.com/history/boeing/c97.html
Actually these were nice planes. It says it could dispense that amount of fuel and carry the troopls.
And fly 4,300 miles. The average jet would have to burn what the 4360's would plus the amount they were carrying to dispense, to fly that distance.

The engine that became the JT-8D in commercial usage started out as the power for the HOUND DOG standoff missile carried by B-52's and was designed for 2 hours max operating time. Very early JT-8's averaged about 100 hours BTO, mostly because of burner can scaling. P&W kept improving and improving the engine until it was certified to operate over 25000 hours BTO. Early JT-9's on 747's had horrible reliability issues (Boeing flew RA 004 to Paris for the airshow, changed engines and flew back to Everett and changed engines again in 1969) .


Modern turbine engines usually have no in service hour limits and 'run until failure' they also are more and more being built modular so if a section has a problem , that unit can be replaced and the engine continues in service and that is now getting down to self contained oil supplies for each section of the engine so chips from one place don't shell the entire engine. The GE 90 on the 777 in over 3 MILLION hours of in service has, fleet wide replaced exactly 3 inlet blades due to impact damage and they are 6 feet long, made of CFRP, and have metal leading edges. The TRENT issue with the 777 in London came about as a design issue wherein the fuel inlet line didn't have enough insulation and the fuel jelled in the nacelle prior to getting to the fuel control (MEC), that issue has been addressed by R/R.

Somewhere in my crap. I still have the CAM 18 (publish date 1949) I had to buy when I was in A&P school somewhere over six or seven weeks ago (actually 45 years ago) that clearly stated that 'jet engines will never become practical in commercial usage due to very high specific fuel burn and reliability issues' and that's straight from your government and its 'experts' (some other expert stated that it would be totally impossible for any wheel driven car to exceed 165 MPH in a quarter mile from a standing start, that was published about 6 days after the new E.T. and speed record was set at 185 MPH back in the 1950's)

Modern jet engines do not 'just blow' within a few hours of entering service, and anything you'd care to know about failure rates and reliabilities can be found in the FAA website, all that stuff has to be open and in the public domain by law. A contributing factor in the increase of reported bird strikes is the fact that engines now are huge! A GE 90 on a 777 is 13 feet in inside diameter, thats bigger than the outside circumference of a 737 fuselage, bigger hole, more likely that TWEETY is going in. New very high bypass engines send around 95% of all air taken into the inlet around the outside of the nacelle and create 'cold thrust' just enough air goes into the hot part of the engine to maintain the bonfire and keep the fuel burning, that explains the hard shreek you hear as a newer big engine passes you on the ground, it's air going around the engine shearing as it expands leaving the aft lip of the fan cowl nacelle (the ulitmate example of blowing across the neck of an empty bottle), the GEnxt on the 787 has 'cookie cutters' or 'sharks teeth' on the trailing edge of the fan cowls to virtually eliminate all the climbout screech you hear.

The guys who do major overhauls on CF-6 engines have discovered that over 98% of all 'engine fails to operate within limits' off wings are the result of some mechanic incorrectly adjusting the settings on the engine MEC (main engine control) it takes about 7 or 8 minutes to adjust one correctly and the engine is yellow tag/RTS and 'run until failure', it's like you reaching in under your old cars hood and giving the air bleed screw on the carburetor (for those of you under 30, please study your tablets on ancient reciprocating engine fuel delivery systems) a couple of random turns and then bitching because the car runs like junk.

So please remove your tinfoil hat on this subject.

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Don't make me go get my flying monkeys-

Oh, and a few years ago, a 777-300ER flew somewhat over 23 continuous hours and from Singapore the I believe London (around 12000 miles)to set the all time distance record for airliners, including several hours operating above 40000 feet with one engine shut down. They took something like 5 complete flight test crews to cover all the flying hours plus a lot of press people.

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Don't make me go get my flying monkeys-

(Sorry for jumping in, Inspector )

Just for clarification:

"Run until failure" doesn't necessarily mean "run until it quits." These engines are subject to inspections and trend monitoring that can often detect failures or pending failures long before they would cause an issue in flight (in flight shutdown.) As you point out, actual engine shutdowns in flight are very rare events. It's safe to say that the majority of airline pilots will not experience an inflight shutdown in their career.

An offhand guess (I don't have the statistics) is that most jet engines go between somewhere between 5000 and 10,000 hours between being changed. But I think actual inflight shutdown rates are on the order of 2 or 3 per 100,000 hours of operation. (.002 or .003 per thousand hours.)

Anecdotally, early in my career I flew with many pilots who had been around for the transition from props to jets. Even with the early jets, they all noted that ingine shutdowns went from fairy common events (several per year....."Feather #3....) to rare events. More than a few of these "old timers" had never shut down a jet engine inflight.

Best,

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Steve
www.eaglesmereairmuseum.org
www.net2nite.com

Not a problem airplanejunkie, thanks for the extra information.

I failed to mention that new airliners have on board condition monitoring programs and the airplane can detect an impending issue, send the appropriate message to maintenance control, and in some cases advise the maint cont where the nearest replacement part is in the system, get that part routed, and do the scheduling so at the next weekend check or overnight the work order spews out of the computer along with the other scheduled items on the 'A' or 'B' check printouts. The 777 has an onboard laptop computer that has 5 external download ports on the aircraft for troubleshooting, it's carried in the flight deck. Unfortunately the physics of trying to convert 'Speed of light' info from the aircrafts ARINC databusses to copper(the plug in port) to the laptop sometimes makes the troubleshooting a long and veeerrrryyyyssslllllooooowww process so the maintenance people will go to the flight deck and do preliminary checks off the EIFIS screens then go to the affected systems analysis point in the aircraft.

Years ago, the DC-10 had two sets of manuals the TAFI (turn around fault isolation manuals) was @ each station, and we're talking big, heavy, thick binders, for the maintenance folks to do logical troubleshooting ('light does not go on, check lightbulb' sounds stupid but it happens- a lot) and the FEFI (flight environment fault isolation manual) which was an onboard QRM for the flight engineer to use to narrow down the area of a problem while in flight so maintenance could show up with the right tools and equipment and turn the problem in a rapid time frame. Douglas/Mac Doug also used to print LAMM manuals for each customer. These were system by system sort of cartoon type bound QRM (quick reference manuals) usually about an inch or two thick and the size of regualr paper. They were wonderful for helping figure out how a system worked and where the major components were in that system, all done ATA chapter style. It's just a shame that when the two companies merged, Boeing decided to discontinue them due to NIH mentality.

In service there are lots of cases of 30000+ hour engines that have never been OTW since the airframe left the manufacturer and you are right it's not 'run 'er till she blows'

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Don't make me go get my flying monkeys-

When I become emperor, each airline will be required to have a few vintage prop planes as part of it's fleet. Now we'll still allow jets, just in case you have no taste or are in a hurry to get somewhere faster, safer, and cheaper, kind of like a Fedex overnight package.

But for those of us who don't go to Target for the ambiance, wouldn't it be great to have the option of booking your flight to SUN N FUN on a Connie or a Merlin engined DC-4? And for anything up to about 200 miles, you find more comfort and headroom on a DC-3.

There might be few real pilots around who can still fly these things.

And since you don't need a gateway to load and unload, the airlines would have one less excuse to maroon people on the tarmac.

And don't sweat it, when I am in charge there will less bannings on WiX. Some reeducation camps may be necessary for a few of you and once past that, a small surcharge on each word you write. You know who you are.

.

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Bill Greenwood
Spitfire N308WK

I'm currently working on an RB-211 (powerplant for 757 and various other jetliners) with over 18,000 hours on it since a shop visit. A year or so ago our company removed a CF6-80C2 from a 767-300 with over 40,000 hours before removal, having been delivered from Boeing on that airplane. A fair record considering how fragile folks think turbine engines are. Don't get me wrong, I'd rather be working on the "other" round engines for a living, but the designers, builders, operators, and maintainers have come a long way since the Whittle and Heinkel powerplants.

Bill, I like where you're going with the propliners in each fleet. We've already got one DC-3 done and Tulsaboy is getting a second started, so it looks like a sub-fleet is in the making!

S

Sign me up for the "vintage fleet." Where do I send my resume, Your Emperorness? (or is it Your Airworthiness?)

For sure a Ford Trimotor type rating is on my bucket list, and I know a DC3 type rating is on my wife's list.

As far as engine time on the airframe goes, I had no idea they were going as long as 40K hours or more. Wow!

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Steve
www.eaglesmereairmuseum.org
www.net2nite.com

Anybody know where I can get a few hours as a passenger in a DC-3? I could use being lulled to sleep by a pair of 1830's again, been a long, long time-

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Don't make me go get my flying monkeys-