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Mike Oxbig
14th Jan 2010, 16:06
I have recently moved aircraft types and am now flying one which allows flex take offs and when programing the autothrottle allows you to choose a V1. What are the advantages of choosing V1 min over V1 max or vice versa? Is it a bit like taking off with more/less flap?

V1 min gives you a shorter TORR and consequently shorter stopping distance but then you are at a lower airspeed after unstick whereas V1 max is the opposite. Should one always choose V1 max on longer runways? Are there any other factors I should be thinking about as well?

Thanks.

hetfield
14th Jan 2010, 16:21
I would say

Stop limited - lower V1
Go limited - higher V1

CAT1 REVERSION
14th Jan 2010, 17:38
Check your Vmcg.....In-particular against an artificial increase in V1 to say 120kts in Wet Conditions!! (usually only an issue on mid length R/W's)...

V1 min will decrease your screen height
V1 max will increase your screen height

PERF A.....Both should give you obstacle clearance, but do you really want to reduce your screen height (35') at shorter airlfields....?

FE Hoppy
14th Jan 2010, 19:08
unless you have obstacles I would go with MIN every time. Lot's a failed rejected take offs to read about, not very many cases of hitting stuff after take off.

Err on the side of safety if I was you.

alatriste
14th Jan 2010, 20:02
Some Gross wight charts or RTOWs offer the oportunity to operate with a range of V1 when taking off from a runway longer than needed.
V1 max will be limited by ASDA or TORA (if SWY not available)
V1 min will be limited by TODA or TORA (if CWY not available)
The bigger the diference between runway needed and available the wider the range.
Anyhow, V1 must comply with limitations regarding Vmcg and Vmbe.
Prior the take-off only ONE (not a range) V1 must be chosen.

A very nice explantion can be found on "Getting to grips with aircraft performance" from Airbus. Look at SmartCockpit - Airline training guides, Aviation, Operations, Safety (http://www.smartcockpit.com) at Flight OPS/performance/ "Understanding V1 Range" from Boeing.

REGARDS.

Pugilistic Animus
14th Jan 2010, 21:31
Nows here's a topic worthy of a pprune discussion from J_T, O_S and Mutt:ok:

PA:)

john_tullamarine
14th Jan 2010, 23:01
Some interesting ideas floating around in this thread .. first ..

V1 min gives you a shorter TORR and consequently shorter stopping distance but then you are at a lower airspeed after unstick whereas V1 max is the opposite.

...can we revisit and provide some further comment on these thoughts ?