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V-speed Definition Question  
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Posted (2 years 3 months 1 day 14 hours ago) and read 3483 times:

I'm reading "Handling the Big Jets" and Davies defines V3 and V4 as follows:
- V3 - The all engines screen speed; the speed at which the aeroplane is assumed to pass through the screen height with all engines operating on take-off.
- V4 - The all engines steady initial climb speed; the speed assumed for the first segment noise abatement take-off procedure.

However Wikipedia and other sources say:
- V3 - Flap retraction speed.
- V4 - Steady initial climb speed. The all engines operating take-off climb speed used to the point where acceleration to flap retraction speed is initiated. Should be attained by a gross height of 400 feet.


Which one is correct? Yes I realize Handling the Big Jets was last revised in 1971.  


"There are no stupid questions, but there are a lot of inquisitive idiots."
6 replies: All unread, jump to last
 
User currently offlineegph From United Kingdom, joined Feb 2006, 242 posts, RR: 0
Reply 1, posted (2 years 2 months 3 weeks 5 days 10 hours ago) and read 3167 times:

The Wikipedia article to which you refer cites a current Transport Canada webpage as its source for V3 and V4 definitions. So it comes down to whether you trust a current Transport Canada source or a book last reviewed before some of today's pilots were even born.

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 2, posted (2 years 2 months 3 weeks 5 days 9 hours ago) and read 3158 times:

Quoting egph (Reply 1):
So it comes down to whether you trust a current Transport Canada source or a book last reviewed before some of today's pilots were even born.

Fair point. But basically then we're saying this is about various regulatory authorities language interpretation? 

BTW said book also calls "angle of attack" "angle of incidence", said I have heard describe the angle of mounting of the wing.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 3, posted (2 years 2 months 3 weeks 4 days 21 hours ago) and read 2965 times:

Poteyto potahto...

V3 and V4 are not universally used like 1 and 2. They dont quite need the same stringent definition.



The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlinevikkyvik From United States of America, joined Jul 2003, 9945 posts, RR: 26
Reply 4, posted (2 years 2 months 3 weeks 4 days 17 hours ago) and read 2914 times:
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Quoting Starlionblue (Thread starter):

That's interesting - so by the Wikipedia definition, you'd reach V4 before V3?

Quoting Starlionblue (Reply 2):
BTW said book also calls "angle of attack" "angle of incidence", said I have heard describe the angle of mounting of the wing.

Interesting - I've never heard AoA refer to anything but the angle of the wing with respect to the freestream flow. Similarly, I've never heard AoI refer to anything but the mounting angle of the wing.



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User currently offlineDavid L From United Kingdom, joined May 1999, 9524 posts, RR: 42
Reply 5, posted (2 years 2 months 3 weeks 4 days 13 hours ago) and read 2852 times:

Quoting vikkyvik (Reply 4):
Quoting Starlionblue (Reply 2):BTW said book also calls "angle of attack" "angle of incidence", said I have heard describe the angle of mounting of the wing.
Interesting - I've never heard AoA refer to anything but the angle of the wing with respect to the freestream flow. Similarly, I've never heard AoI refer to anything but the mounting angle of the wing.

I've seen this come up in discussions before. While I don't remember anyone justifying it, I think the general reaction was to cut him some slack because the context makes it clearer and because of the quality of the work - i.e. you just have to "power through" that aspect.


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17030 posts, RR: 67
Reply 6, posted (2 years 2 months 3 weeks 4 days 12 hours ago) and read 2841 times:

Quoting David L (Reply 5):
Quoting vikkyvik (Reply 4):
Quoting Starlionblue (Reply 2):BTW said book also calls "angle of attack" "angle of incidence", said I have heard describe the angle of mounting of the wing.
Interesting - I've never heard AoA refer to anything but the angle of the wing with respect to the freestream flow. Similarly, I've never heard AoI refer to anything but the mounting angle of the wing.

I've seen this come up in discussions before. While I don't remember anyone justifying it, I think the general reaction was to cut him some slack because the context makes it clearer and because of the quality of the work - i.e. you just have to "power through" that aspect.

Truth be told, I'd never heard the terms used for anything else either.

The book is more or less legendary and certainly the gentleman writing it seems to have been quite a character. I can't find any records on him easily googlable but I bet he was flying during WWII and then went on into flight test without ever raising his voice once. The way he describes what must have been quite harrowing flight tests in passing and with withering understatement is a pure pleasure. This was way before CFD and all that so who knew what would really happen. This is truly writing from before the PC age, when men were men and women were secretaries. No excuses, no pandering to sensitivities, just a clear message.

I'm with David. The book is so good that I suppose cutting the man some slack for archaic terminology is warranted. As someone on PPrune said (I paraphrase): "You have no idea how hard the man worked to make the craft you are flying safe."



"There are no stupid questions, but there are a lot of inquisitive idiots."
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