Re: Pending new revised Sky Arrow POH, revised Operating Limitations and SB
Posted: Mon Dec 25, 2017 2:17 pm
As the Doctor says
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Also my understanding is that indicated speeds are a more direct measure of what air pressure in actually on the airframe (e.g. loads) than TAS.drseti wrote:All the V speeds are based upon indicated. That's the only information readily available to the pilot in flight.CharlieTango wrote:Using indicated or true?
Are you suggesting I shouldn't be using Harbor Freight nuts and bolts?MrMorden wrote:Now if one is built with AN hardware and the other with Harbor Freight nuts and bolts...
We encounter this in the Europa, Descending from 16,000' we easily exceed Vne at TAS. I'm told flutter don't care about IAS its about TAS so we slow below Vne indicated.MrMorden wrote:Also my understanding is that indicated speeds are a more direct measure of what air pressure in actually on the airframe (e.g. loads) than TAS.drseti wrote:All the V speeds are based upon indicated. That's the only information readily available to the pilot in flight.CharlieTango wrote:Using indicated or true?
My CT has a Vne of 145KIAS. It’s easy to exceed 145kt in a descent in TAS yet still be under 145kt IAS. I have assumed this is safe. If I get close to Vne IAS the airplane lets me know with lots of wind noise, and seems not to like that much. I get no such indicators when exceeding Vne TAS, it stays smooth.CharlieTango wrote:We encounter this in the Europa, Descending from 16,000' we easily exceed Vne at TAS. I'm told flutter don't care about IAS its about TAS so we slow below Vne indicated.MrMorden wrote:Also my understanding is that indicated speeds are a more direct measure of what air pressure in actually on the airframe (e.g. loads) than TAS.drseti wrote:
All the V speeds are based upon indicated. That's the only information readily available to the pilot in flight.
I can see no flaw in your reasoning.MrMorden wrote:
Am I incorrect there?
Yes you are, sorry Andy. Flutter is one of 2 things in aviation that happen suddenly with no buildup. There is no warning hence we need a Vne to provide a speed with a safe margin. Many designs base there Vne on flutter but LSA are not subject to conclusive testing so even additional margin is needed.MrMorden wrote:My CT has a Vne of 145KIAS. It’s easy to exceed 145kt in a descent in TAS yet still be under 145kt IAS. I have assumed this is safe. If I get close to Vne IAS the airplane lets me know with lots of wind noise, and seems not to like that much. I get no such indicators when exceeding Vne TAS, it stays smooth.CharlieTango wrote:We encounter this in the Europa, Descending from 16,000' we easily exceed Vne at TAS. I'm told flutter don't care about IAS its about TAS so we slow below Vne indicated.MrMorden wrote:
Also my understanding is that indicated speeds are a more direct measure of what air pressure in actually on the airframe (e.g. loads) than TAS.
I was given to understand V speeds are in IAS because they better represent the actual pressures, and thus loads, on the airframe. After all, the TAS at higher altitudes could be high, which represents the total speed through the airmass, but IAS might be lower, and indicates the actual drag pressure exerted on the airframe.
Am I incorrect there?
Flutter is about harmonics not pressure building on the airframe. Vne at IAS in Part 23 certified aircraft does not provide adequate margin for flutter at all altitudes.drseti wrote:I can see no flaw in your reasoning.MrMorden wrote:
Am I incorrect there?
Well, I have experienced tail flutter in my CT. It does come on quickly, but not instantly. I had time to slow down. BTW this happened at WELL below Vne, and was due to a manufacturing issue in a few CTs and has been corrected.CharlieTango wrote:Yes you are, sorry Andy. Flutter is one of 2 things in aviation that happen suddenly with no buildup. There is no warning hence we need a Vne to provide a speed with a safe margin. Many designs base there Vne on flutter but LSA are not subject to conclusive testing so even additional margin is needed.MrMorden wrote:My CT has a Vne of 145KIAS. It’s easy to exceed 145kt in a descent in TAS yet still be under 145kt IAS. I have assumed this is safe. If I get close to Vne IAS the airplane lets me know with lots of wind noise, and seems not to like that much. I get no such indicators when exceeding Vne TAS, it stays smooth.CharlieTango wrote:
We encounter this in the Europa, Descending from 16,000' we easily exceed Vne at TAS. I'm told flutter don't care about IAS its about TAS so we slow below Vne indicated.
I was given to understand V speeds are in IAS because they better represent the actual pressures, and thus loads, on the airframe. After all, the TAS at higher altitudes could be high, which represents the total speed through the airmass, but IAS might be lower, and indicates the actual drag pressure exerted on the airframe.
Am I incorrect there?
Those articles imdicate that TAS makes more sense at high altitudes, which agrees with Pipestrel. So it might make a difference to you, at your 14,0000ft+ cruise level at the upper limits in descent. To me as a flatlander sport pilot, I think I am safe at 10,000 and below level using IAS exclusively. In fact I know I am — I did a descent on Tuesday from 6500ft under power and hit 154KTAS and 122KIAS with no issue at all.CharlieTango wrote:Flutter is about harmonics not pressure building on the airframe. Vne at IAS in Part 23 certified aircraft does not provide adequate margin for flutter at all altitudes.drseti wrote:I can see no flaw in your reasoning.MrMorden wrote:
Am I incorrect there?
http://www.australianflying.com.au/news ... -explained
https://www.flyingmag.com/technique/pro ... ling-lucky
https://mooneyspace.com/topic/11013-vne ... d-flutter/
http://www.atpforum.eu/forum/technical- ... ion-of-tas
TAS is a major consideration in Vne. Only planes we can't afford have the design and testing to provide a well defined envelope. That would be Vne at IAS up to service ceiling. For most of us we don't have as well a defined limit.MrMorden wrote:Those articles imdicate that TAS makes more sense at high altitudes, which agrees with Pipestrel. So it might make a difference to you, at your 14,0000ft+ cruise level at the upper limits in descent. To me as a flatlander sport pilot, I think I am safe at 10,000 and below level using IAS exclusively. In fact I know I am — I did a descent on Tuesday from 6500ft under power and hit 154KTAS and 122KIAS with no issue at all.CharlieTango wrote:Flutter is about harmonics not pressure building on the airframe. Vne at IAS in Part 23 certified aircraft does not provide adequate margin for flutter at all altitudes.drseti wrote:
I can see no flaw in your reasoning.
http://www.australianflying.com.au/news ... -explained
https://www.flyingmag.com/technique/pro ... ling-lucky
https://mooneyspace.com/topic/11013-vne ... d-flutter/
http://www.atpforum.eu/forum/technical- ... ion-of-tas