why did you not trust the POH, and fly the (weight corrected) approch speeds in the manual?
Two reasons:-
The POH speed values are all MTOW, there are no weight corrected published values, although these could be extrapolated, but that in conjunction with a best guesstimate on actual weight for each flight still leaves you with an estimated set of speeds. I like some degree of certainty when this close to the envelope.
Secondly, my aircraft has an STC conversion applied to it, making it a hybrid. Rocket Engineering never re-certified many of the performance numbers, simply choosing to defer to the original piston model speeds, and relying on one magic number of 90kts for full flap approach, which gives a big safety margin. I can understand why they chose this easier path from a paperwork point of view, but clearly it is not a reflection of what the aircraft is actually capable of achieving.
Having a reliable way to explore this envelope allows me to obtain maximum utility out of my aircraft.
So far l have only been exploring the slowest approach speed with the AOAI. There are other dimensions to this technology, such as maximum performance climbs, steep turn stall margins. These are all dynamic based on weight and other factors. I like the idea of having real time measurement based on the current state of the aircraft rather than trying to work it out and adding in 5kts for the mother in law!
E
FWIW I’ve just had the Garmin GI 260 installed. The reason I chose it over the Aspen firmware upgrade is the audio output.
Looking forward to hearing your review of its operation Chris.
E
@eal,
Ok so basically because the POH is inadequate and does not provide any useful approach speeds below 90kt, which at Vs plus 50% is too fast by 10kt even at MTOW. Understandable considering a formal flight test programme to establish performance data is expensive, and that their target market is full of long runways.
What did they do to the landing performance charts?
Some per(s)nickety character will be along shortly pointing out that by flying slower than 90kt on approach is “illegal” you are “violating” the holy POH, you will be uninsured you and your children and children’s children for three generations will all die horribly.
Vs plus 30% plus additions for gusts is not really close to the envelope, the one maneuvre where you are closest to it near the ground is a Vx climb, where on an overpowered machine like the Jetprop the stall warner is probably close to going off. Definitely an AOA indicator would be useful there.
What is the display lag for this technology? The “formula” must take into account pitch (pretty much instantaneous), and the aircraft trajectory (airspeed – again very quick, and rate of climb – slightly slower). So it aught to be very good when adjusting pitch, but a bit laggy in gusts / when vertical speed changes are involved. And how does it work in turns? Does it take G-force into account?
According to the blurb, Aspen also make use of the built in accelerometers, so l assume that takes care of the G factor.
E
eal wrote:
Looking forward to hearing your review of its operation Chris.
I’ll make a little video in the new year when I’ve shaken off this cold…
@chrisparker, so that is the unit with an angle of attack probe?
@eal, yours is purely calculated based on ADC and AHRS data (with aircraft weight input I assume)?
so that is the unit with an angle of attack probe?
Yes, heated probe.
@eal, yours is purely calculated based on ADC and AHRS data (with aircraft weight input I assume)?
In essence correct, although l believe there is accelerator input in the mix as well. Various weights are input as part of the initial calibration flight only. After that there is no further input from the pilot.
I flew into a very short strip (550 M) today at different weights as it happens, with a 5kt tailwind; landing purely by reference to the AOAI instead of the ASI, although l did have a safety pilot calling out the air speeds as a back up, and it was noticeable how much better the slower approach speed worked out.
E
I flew into my regular short field solely relying on the AOA yesterday. I had a safety pilot calling out the airspeeds, but I was pegging the lift reserve instead of the airspeed.
This was the touch down, around 78 Kts, considerably slower then normal. Love it!
