Jim Burns[_2_]
May 16th 07, 08:32 PM
The latest issue of AOPA Pilot contains an article about vortex generators.
The article places high emphasis on how they can improve controllability
during low airspeed single engine operations in twin engine airplanes. The
subtitle of the article, as it relates to twins, mentions "Blueline Ops or
Vmc". The article then repeatedly associates "blue line" with Vmc rather
than RED line with Vmc.
For the single engine pilot this article can lead to serious
mis-information. Multi engine airplanes typically have two additional
indicators on their ASI. The first is a radial red line, an indicator Vmc,
the indicated airspeed which a pilot will experience minimal control during
single engine operations under a set of specific criteria. The second
additional indicator is a radial blue line which indicates Vyse, or best
rate of climb under single engine operations under a set of specific
criteria.
For instance, the redline of our Aztec is 80mph. If we loose our critical
(left) engine, at gross weight, a rear most CG, full power on the right
engine, ect, ect... we can expect to loose directional control if our
airspeed drops below 80mph. This is where vortex generators could help, by
reducing the Vmc airspeed if all other conditions remained the same. Red
line is the "goal for control".
On the other hand, our Aztec has a radial blueline at 102mph. If we loose
an engine, at gross weight, our best rate of climb (with our single
operating engine at full power, our airplane in it's optimal configuration
and in standard conditions) would be at 102mph. Vortex generators, as
related to Vyse, was not the subject of the article, although it would be an
interesting subject. Blue line is the "goal for performance" (climb,
maintaining, or loosening the least altitude)
The references to "blueline" in the AOPA Pilot article clearly should
instead refer to "redline" when referencing Vmc and single engine control
issues with multi engine airplanes.
Jim
The article places high emphasis on how they can improve controllability
during low airspeed single engine operations in twin engine airplanes. The
subtitle of the article, as it relates to twins, mentions "Blueline Ops or
Vmc". The article then repeatedly associates "blue line" with Vmc rather
than RED line with Vmc.
For the single engine pilot this article can lead to serious
mis-information. Multi engine airplanes typically have two additional
indicators on their ASI. The first is a radial red line, an indicator Vmc,
the indicated airspeed which a pilot will experience minimal control during
single engine operations under a set of specific criteria. The second
additional indicator is a radial blue line which indicates Vyse, or best
rate of climb under single engine operations under a set of specific
criteria.
For instance, the redline of our Aztec is 80mph. If we loose our critical
(left) engine, at gross weight, a rear most CG, full power on the right
engine, ect, ect... we can expect to loose directional control if our
airspeed drops below 80mph. This is where vortex generators could help, by
reducing the Vmc airspeed if all other conditions remained the same. Red
line is the "goal for control".
On the other hand, our Aztec has a radial blueline at 102mph. If we loose
an engine, at gross weight, our best rate of climb (with our single
operating engine at full power, our airplane in it's optimal configuration
and in standard conditions) would be at 102mph. Vortex generators, as
related to Vyse, was not the subject of the article, although it would be an
interesting subject. Blue line is the "goal for performance" (climb,
maintaining, or loosening the least altitude)
The references to "blueline" in the AOPA Pilot article clearly should
instead refer to "redline" when referencing Vmc and single engine control
issues with multi engine airplanes.
Jim