Blue line speed on an Aztec
Blue line speed on an Aztec
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Join Date: Apr 2000
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Cheers Speedbraker.
The speeds for operation that I have been given are
Vr 70
unstick 77
initial climb 100
cruise climb 110
I know the Seneca III's blue line is 92 knots, so I am worried that 88 sounds a bit low.
Can anyone else confirm Speedbrakers figure?
Any response is much appreciated
The speeds for operation that I have been given are
Vr 70
unstick 77
initial climb 100
cruise climb 110
I know the Seneca III's blue line is 92 knots, so I am worried that 88 sounds a bit low.
Can anyone else confirm Speedbrakers figure?
Any response is much appreciated
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A few decades since I was in an Aztec so the memory of the specific numbers is non-existent.
It is worth keeping in mind a few points
(a) the POH quoted speed is generally for max weight standard sea level conditions and the "real" figure will vary at other test points. Some aircraft manuals have multiple figures to address these variations.
(b) in the real world, it is very easy to lose speed and rather difficult to claw it back, so better to be a little faster than slower.
(c) in the real world for a light twin (especially a US below 6000lb twin), the OEI climb capability is more imagined than real.
(d) one of the very real dangers in the GA training environment is that training and testing usually is done at comparatively low weights which see the aircraft doing not all that badly.... but try it at a DH of, say, 6000 feet and at max weight and the story is very different. The danger lies in the subtle training reinforcement in the pilot's mind that this class of aircraft goes fine on one motor ... this is most definitely not the case.
[ 05 September 2001: Message edited by: john_tullamarine ]
It is worth keeping in mind a few points
(a) the POH quoted speed is generally for max weight standard sea level conditions and the "real" figure will vary at other test points. Some aircraft manuals have multiple figures to address these variations.
(b) in the real world, it is very easy to lose speed and rather difficult to claw it back, so better to be a little faster than slower.
(c) in the real world for a light twin (especially a US below 6000lb twin), the OEI climb capability is more imagined than real.
(d) one of the very real dangers in the GA training environment is that training and testing usually is done at comparatively low weights which see the aircraft doing not all that badly.... but try it at a DH of, say, 6000 feet and at max weight and the story is very different. The danger lies in the subtle training reinforcement in the pilot's mind that this class of aircraft goes fine on one motor ... this is most definitely not the case.
[ 05 September 2001: Message edited by: john_tullamarine ]
Join Date: Mar 2001
Location: Lookout Mtn Tennessee
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wonder how many accidents are caused by these speeds being painted on the asi, and not calculated by the pilot for given conditions....why is a speed that is applicable only for one specific set of conditions...(rarely encountered) painted on the asi, when it is mostly irrelevent?
Multi-engine aircraft are divided by FAR 23 into two weight classes - above and below 6000lbs, and those below 6000lbs are divided into two classes depending on Vso (stall speed in the landing configuration) above and below 61 knots CAS.
Only those twins that weigh more than 6000lbs or have a Vso higher than 61 knots need to demonstrate any single-engine climb performance at all for certificaion, and the requirements are pretty meager. Basically the regulation says that these aircraft must demonstrate a single engine capability at 5000' (ISA) with the inop engine feathered and in a clean configaration.
The only requirement for an aircraft less than 6000lbs, and with a Vso less than 61kts (like the Aztec) is that its climb performance (positive or negative) be determined.
There is nothing in the FAR which says an aircraft must fly while in the take-off configuration with one engine inop.
Talking about rotation, manufacturers tend to have a philosophy about this that shows up in in the aircraft design, wing incidence and gear positioning.
Piper recommends that most twins be rotated at Vmc, Cessna on the other hand suggests a lift off at a speed much higher than Vmc and very close to best single-engine angle of climb speed. In the case of a C-310, Vmc is 75 knots, recommended rotation speed is 91 knots and best single engine angle of climb speed is 94.
Try and hold a Seneca or Aztec on the ground much beyond Vmc plus 5 knots (zero flap) and the aircraft will begin to wheelbarrow! Cessna twins (and most cabin class twins) will happily stay on the ground for much longer than that.
A Navajo for instance (stretching the old memory) will happily go by road, if you don't positively rotate it - you hardly have to "force the aircraft on the runway well past VR and until a few knots past Blue Line"!
I would rotate a light (FAR 23) twin not below Vmc+5 (or the recommended rotate), and I pull the gear up just after getting airbourne, then climb at the best all engine climb rate (which is faster then blue line) until clear of obstacles in the area.
(Information from an old post of mine)
Only those twins that weigh more than 6000lbs or have a Vso higher than 61 knots need to demonstrate any single-engine climb performance at all for certificaion, and the requirements are pretty meager. Basically the regulation says that these aircraft must demonstrate a single engine capability at 5000' (ISA) with the inop engine feathered and in a clean configaration.
The only requirement for an aircraft less than 6000lbs, and with a Vso less than 61kts (like the Aztec) is that its climb performance (positive or negative) be determined.
There is nothing in the FAR which says an aircraft must fly while in the take-off configuration with one engine inop.
Talking about rotation, manufacturers tend to have a philosophy about this that shows up in in the aircraft design, wing incidence and gear positioning.
Piper recommends that most twins be rotated at Vmc, Cessna on the other hand suggests a lift off at a speed much higher than Vmc and very close to best single-engine angle of climb speed. In the case of a C-310, Vmc is 75 knots, recommended rotation speed is 91 knots and best single engine angle of climb speed is 94.
Try and hold a Seneca or Aztec on the ground much beyond Vmc plus 5 knots (zero flap) and the aircraft will begin to wheelbarrow! Cessna twins (and most cabin class twins) will happily stay on the ground for much longer than that.
A Navajo for instance (stretching the old memory) will happily go by road, if you don't positively rotate it - you hardly have to "force the aircraft on the runway well past VR and until a few knots past Blue Line"!
I would rotate a light (FAR 23) twin not below Vmc+5 (or the recommended rotate), and I pull the gear up just after getting airbourne, then climb at the best all engine climb rate (which is faster then blue line) until clear of obstacles in the area.
(Information from an old post of mine)
