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Author Topic: "Pushing the envelope"
FFFF
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posted 12-25-1999 05:48 PM       Edit/Delete Post   Reply With Quote
Does this expression have anything to do with jets?
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mane_raptor
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posted 12-25-1999 06:14 PM     Profile for mane_raptor   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Nah...just postal worker jargon, that's all!!

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Check six & aim for the cockpit.


Posts: 6145 | From: Maine USA, Proud Member of ELF (EAW Liberation Front) | Registered: Nov 1999  |  IP: Logged
Envelope
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posted 12-25-1999 09:20 PM     Profile for Envelope   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
I feel obligated to answer that. I study mathematics, so you would think I know what the word means - exactly. But, the truth is the best description I have heard so far was in the Tom Wolfe novel "the Right Stuff". The way I remember it is that it represents those trajectories for an airplane that represent controlled flight.

I suspect that the mathematics around this concept are called Hamiltonian mechanics. In Hamiltonian mechanics, position in three demensions changes with time and so is a trajectory in three dimensional space - a curve in space. The rate of change of this trajectory is the velocity. But the velocity also changes with time and this relates to the energy being applied to or dissipated from the aircraft. Since the velocity changes with time in combinations of the three dimensions it also can be represented as a curve in three dimensional space. So you have two three dimensional spaces representing the flight of an airplane and, indeed, anything with mass moving through space. The two spaces together are called the "phase space". My guess is that the abstract space of all possible trajectories of controlled flight of an airplane is the "flight envelope". I've never seen this described in mathematical literature, but it fits the novel's description.

[This message has been edited by Envelope (edited 12-25-1999).]


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mane_raptor
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posted 12-25-1999 09:37 PM     Profile for mane_raptor   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
That's all vey well Mr E., but I still say it's postal jargon. As a former postal worker (got kicked out because I couldn't qualify on the range), I do believe that you folks stole that from us. Look I'm not going to get into an argument here, I just stating a fact.

Now where did I put the AK47?

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Check six & aim for the cockpit.

[This message has been edited by mane_raptor (edited 12-25-1999).]


Posts: 6145 | From: Maine USA, Proud Member of ELF (EAW Liberation Front) | Registered: Nov 1999  |  IP: Logged
FALCON
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posted 12-25-1999 09:38 PM     Profile for FALCON   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Pushing the limit
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Simmer
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posted 12-25-1999 10:57 PM       Edit/Delete Post   Reply With Quote
It is a theoretical envelope depicted in 2 dimensions...The only sims (though very very light) that showed you the envelope while in flight was Janes ATFG, USNF and Fighter Anthology...It wasnt that accurate but you could understand the concept.

Pushing the envelope is operating your aircraft on the fringe (border) of this theoretical flight envelope.


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nick moyrand
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posted 12-26-1999 03:48 AM     Profile for nick moyrand   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
I'm with Mane Raptor on that one, the term comes from guys retiring from active flight duty in the USAF and joining the postal services.

As the term implies, they "started pushing envelopes" to avoid getting tongue cuts while licking stamps and licking the seams.

As they say, licking envelopes can be much more hazardous than flying fighter jets, hence their move to the postal service.

You know that fighter pilots are basicaly thrill seekers and what better place than the Postal Service to get the ultimate thrill of "pushing the envelope" (and occasionaly, dodging bullets)

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Nick Moyrand


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Major Tom
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posted 12-26-1999 05:31 AM     Profile for Major Tom   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Think of it as overclocking your CPU.

Sometimes it works, sometimes it doesn't.

I knew a girl once who's grand father died in a Sr-71 crash, first one to buy it in one of those machines. They where testing out the maximum potential of the aircraft, there was a 50/50 chance the aircraft could go a little faster, a little higher, than designed. He was a cocky SOB, so he decided to take the risk. The other 50% happened and became a smoking hole in the ground. Interestingly enough the guy in the back actually lived through the ordeal, he ejected alright.

Little higher, little faster, little deader.

I'd sure hate to be the person that flew the F-104's to their limits. I dont know what they nicknamed that beast here, but the Germans called it the widowmaker.


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nick moyrand
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posted 12-26-1999 08:29 AM     Profile for nick moyrand   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
"first one to buy it in one of those machines"

I don't know why but that expression always cracked me up, LOL !

It's really funny 'cause death is one of the only free thing out there.

Also, I don't know of too many guys actualy going out "kicking the bucket". I always wondered as to what it refered to, do you have to kick a bucket on your way out? what if you are paralized, how are you gonna pull that off? what if there is no bucket around, I ask you that!

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Nick Moyrand


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Blaze
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posted 12-26-1999 11:32 AM     Profile for Blaze   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Actually death is not for free, it costs your life ... ;-)
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Andy Bush
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posted 12-27-1999 08:12 PM     Profile for Andy Bush   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
MT

>>I'd sure hate to be the person that flew the F-104's to their limits.<<

It's not that big of a deal. There are three boundaries: stall, max g, and max airspeed. I've been to all three in the 104.

The jet was no widowmaker, despite what the German press called it. I'm very familiar with the Germans and the 104 inasmuch as I was a F-104 instructor in their training program. Most fatalities were either due to pilot error or poor maintenance...as is the case with most a/c.


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JA
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posted 12-27-1999 08:35 PM       Edit/Delete Post   Reply With Quote
Hey Andy - you're talking about the F-104 - wer'e all ears! Maximum speed and g don't seem all that scary as these things go (but what do I know?), but speaking as someone who doesn't know any better, the F-104 looks like it would be terrifying in a stall, due to its tiny wings. Any comments? Thanks for the info!
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Major Tom
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posted 12-28-1999 01:41 AM     Profile for Major Tom   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Did the Germans purchase new F-104's strait from Lockheed or did they buy our "used" ones?

The German guy who was my primary flight instructor said he got in an inverted spin while training a student in a F-104. Now that must have been scary, expecially in the F-104.

I guess the F-104 did get kind of a bad rep when it shouldn't have. I'm sure that the great majority of pilots who flew the plane, didn't feel like the aircraft might spontaniously explode if they looked at it the wrong way.

A lot of planes I suppose got bad reps, sometimes slightly deserved ones, can we say V-tailed doctor killer :-)


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Andy Bush
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posted 12-28-1999 09:01 AM     Profile for Andy Bush   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
JA

The 104 did not stall in the way that most think. Instead, due to the high T-tail design, the a/c would experience a 'pitch-up'. This is a nose-up movement that may be followed by a deparure from controlled flight. I've seen both. What happens next is hard to predict, but if the jet is forced into a prolonged 'departure' condition, it may end up in a spin...similar to what happened to Chuck Yeager. This pitch-up was only a function of angle of attack and therefore could happen at any speed. At high speed, the pitch-up was catastrophic...lots of positive and negative g, followed by extreme gyrations of the jet. From personal experience, I can tell you it is something you only want to do once.

MT

The German 104s were license built in Europe. The a/c that we flew in Arizona were actually built in Europe and then shipped over to the States.

I've never heard of a negative spin in the 104 outside of the original test flights. My suspicion is that the maneuver would be difficult to get into because of the lack of predictability of the departure that precedes the spin.

The airplne 'talked' to you well before the pitch-up happened. There was a device that rattled the stick as a warning...it was called the 'stick shaker'. During normal maneuvers, the stick shaker gave the pilot enough advance warning so that he could back off the g, ie reduce the angle of attack and thereby avoid the departure. It was possible to override the shaker manually...this sometimes resulted in the pilot pushing the jet too far, and it would then pitch-up without further warning. I know this for a fact.(g)

Overall, the 104 was my favorite. Great looks, tremendous performance, and good capability when flown intelligently.

Andy


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Andy Bush
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posted 12-28-1999 09:03 AM     Profile for Andy Bush   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
MT

BTW, what is the name of that German instructor that you flew with?

Andy


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Turbo
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posted 12-28-1999 01:50 PM     Profile for Turbo   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Hey Andy,
When were you stationed at Luke AFB? I was stationed there from '82-'87. Boy, I sure miss those F-104's.

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Major Tom
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posted 12-28-1999 07:59 PM     Profile for Major Tom   Author's Homepage     Send New Private Message   Edit/Delete Post   Reply With Quote
Juergen Tank

not sure if that's spelled right.

He told me about the inverted spin when I asked him "what was the stupidest thing you've ever done in an aircraft." Durring a training flight he let a student go a little to far in an unsuccessfull manuver and somehow wound up in the spin. Must have been one hell of a spin since it was in a F-104.

Juergen said wasn't one mistake that nearly cost him his life, it was a whole bunch of mistakes that where so tiny that he brushed them off. Eventually those mistakes came to a head and very quickly became a deadly serious problem, IE the loss of total control in the aircraft followed by one hell of a spin.

Needless to say that Juergen and the student pilot agreed that maybe this wasn't the best profession for the student to be in.

What was the name of that guy who bought the F-104 and blew it to heck? He used to drive race cars didn't he? Lucky for him he paid extra for a working ejection seat.

I think there might be a few privately owned F-104's in the world, saw one on TLC last night.

One other question Andy, did they actually tell you to pop the drag shute if you got into a real bad stall/spin condition?


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