Blue line airspeed - history of

[aircraft]

Gentlemen and Ladies,

Does anybody know anything of the history of "blue line" airspeed (aka VYSE)?

I am doing a little research and would like to know when it became a certification requirement and the reasons for why it did.

I am well aware of how it is used by current day multi pilots, so please no discussion on modern day use, or discussion about asymmetics in general.

But please, even if you don't know the exact details, I would welcome hearing your thoughts.

My current thinking is that it dates from wartime and the days of the big radials and was there for when you lost an engine in cruise, so giving you the maximum remaining time aloft so as to prepare for the ditching or crash landing.

[411A]

The blue line was not marked on any larger piston transports that I have flown..DC6/7, Lockheed 1649 Constellation, CV440, etc.

And, to the best of my knowledge, it was not marked on light piston twins (ie: FAA requirement) until about 1958 or thereabouts, as I have flown older light twins that were manufactured before then...and it was not marked on the ASI.

[Old Smokey]

The history of taking one engine inoperative performance requirements seriously, with certain guarantees of performance and 'formal' speeds to be flown pre-dates World War II by about 7 years.

That was when Jack Fry, the CEO of TWA, invited tenders for the manufacture of a multi engined airline aircraft capable of losing an engine upon takeoff, and continuing safely to it's destination. The winner was Douglas, who submitted the DC1, which became the DC2, which lead to the DC3, and all of which lead to the establishment of FAR25 as we know it today. Unfortunately, airline CEOs as we know them today are nowhere near Jack Fry's league.

Undoubtedly there were 'recommended' best OEI speeds for aircraft prior to the DC1, but that aircraft marked the turning point whereupon subsequent legislation lead to certain performance guarantees.

In those times they didn't paint pretty colours on aircraft instruments, pilots had to remember the numbers.

Regards,

Old Smokey

[Onan the Clumsy]

Similar threead here (http://www.pprune.com/forums/showthread.php?s=&threadid=167873) in D&G

...oh wait a minute :O :p


Old Smokey Did you see that thing on PBS last night perchance. They spoke about that very moment? Supposedly they wanted to prove the aircraft was worth buying, so they decided to do a take off on one engine :confused: :ooh:

Fortunately common sense intervened and they selected the idle thrust simulation, but they killed it on the climb out and still flew it over the mountains.

[Old Smokey]

Onan,

No, I didn't see it last night, or ever for that matter, I wish that I had. I guess that I'm just guilty of very flukey timing, I'll but a lotto ticket whilst my lucky streak lasts.

Actually, Douglas didn't do it as a sales pitch, but to meet a contract requirement from TWA. The actual demonstration, again, was not done as a Douglas initiative, but as a requirement to demonstrate the contractual requirement. The sale depended upon their meeting the requirement, which was specified before the first design drawings were done.

I was not sure of the moment of actual engine shut-down, legend has it that it was upon lift-off, but legend is legend. I wasn't there, but the TWA contract which pre-dates the design, survives to this day. So too, thousands of passengers survive to this day, due to the foresight of Jack Fry.

Regards,

Old Smokey

[411A]

That particular engine out flight in the DC3 was from Winslow Arizona to Albuquerque, New Mexico.

A very demanding sector, from an engine out performance perspective.

Douglas repeated this flight many years later with the DC-6...with the second engine failed at TOC.
Minimal driftdown noted, believe it or not.
The 'ole DC6 was a very good performer, in high blower.

Now some might ask...how do I know about this?
And the answer is...my Dad was engineering project manager, DC-6, and later, DC-7.

PS: Unless there were two of 'em, I believe it was Jack Fry at TWA....no?

[Old Smokey]

411A,

You're absolutely right. Posts suitably edited to pay due respect to a very decent gentleman.

Best Wishes,

Old Smokey

[john_tullamarine]

aircraft,

Suggest you might have a play in the FAA website .. which has a facility (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/MainFrame?OpenFrameSet) to look at the changing rules over the years ... that should allow you to identify when various things occured.

For instance, a quick looksee just now by yours truly shows that the 23.1545 Vy rule came in at AL 23-3 (11Nov65) when the requirement for marking Vy and Vmc was introduced at FAR 23-1545(b)(5).

A quick look at the Final Rule Making (http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFinalRule.nsf/a09133bddc7f4fbb8525646000609712/f4fbc5f56eaecf63862568a100735640!OpenDocument) for the amendment contains some background which you might find interesting and is the point at which Vx appears to have been cast aside. As an aside, the change is a good example of the "damned if you do, damned if you don't" reality of life ...

Some interesting quotes from this document ..

"Since the regulation will no longer require that the airplane be designed to prevent unintentional spin entry and will no longer require a critical engine inoperative demonstration of lateral and directional control at the stall with the remaining engines at full throttle or maximum continuous power, the Agency believes that the limits of safe single-engine speed should be brought to the attention of the pilots by means of airspeed indicator markings."

.. and this one is quite pertinent to the Vx Vy debate ...

"While the industry recommended that the best angle-of-climb speed (VX) should be included in the marking of the airspeed indicator, the Agency considers that the markings must include the best rate-of-climb speed (VY). VX would be the optimum speed for clearing nearby obstacles under those conditions when the airplane has positive climb. However, VY is considered the key performance speed since it is the speed at which the airplane will be able to maintain the highest possible altitude with one engine inoperative."

Further amendments of relevance came in at 23-23 (01Dec78) and 23-50 (11Mar96) ... I'll leave you to do the hyperlinking thing to read the details on these ...

If the electronic records don't cover the bits you need, then the task becomes one of finding and searching archival regulatory records ... bit of a pain, unless someone reading the thread just happens to know the answer. I have had just this happen ... can recall ringing a regulatory agency years ago and having the call answered by a chap (whom I knew well) from a totally different technical discipline. After the usual g'days and such, he just happened to have, in his bottom drawer, a paper on a question I was chasing .. and this related to something from quite a few years earlier and totally out of his normal ambit .. and he knew it was there and could put his hand on it at a moment's notice .. quite a remarkable and very knowledgeable chap .. and a nice fellow as well.

As indicated in the FAR references above, you will have to troll about in the preceding CARs to make sense of the history ...

Keep in mind that, if you go far enough back, quite a few of the rules have their genesis in engineering guesswork and finger in the wind starting points ... but that would be a whole new and interesting thread, I guess.

All it takes is a bit of Dick Tracey work to track down these sorts of questions and answers ....

... maybe I should really get a life .. ?

[aircraft]

j_t,

Thankyou once again - you've played a blinder!

My questions are now fully answered!

"... maybe I should really get a life .. ?"

- Don't do that! We need you here!


Best regards

Thanks very much to the other contributors.