Suggestion for another EMS gauge

[Doug1]

Hi
Dynon

A nice optional gauge to display on the EMS would be acceleration, based on gps ground speed and indicated airspeed. The units could be metric or imperial.
The usefulness of this gauge would be during the takeoff roll. Each type of aircraft will have typical accelerations required to get the aircraft off the ground in the typical takeoff roll distance at the typical rotate air speed.
By glancing at the acceleration, the pilot has immediate feedback on the takeoff roll required and will allow for runway surface, slope, aircraft elevation, pressure altitude, engine tune, headwind etc.
If during the roll the acceleration is too low, the pilot is immediately aware that the situation is not typical and maybe an abort is required.
An enhancement would be to add typical takeoff roll distance and typical rotate air speed to setup. Now the gauge could calculate during the roll if the typical rotate speed is going to be reached before the end of the typical takeoff roll. If not the gauge may change to to RED, with an option audio warning, "Takeoff roll slow"

For example, with a typical takeoff roll of 200m on a runway length of 500m a red indication on the gauge is of more importance than say on a 1000m runway. Note that the indication will automatically allow for all the variables which can effect takeoff acceleration because the actual airspeed is being used compared with ground speed to see how much of the takeoff roll is being taken.

Doug

 

[Schorsch]

The feature called the speed trend in Skyview (on your IAS tape) could be used for a sense of acceleration

 

[swatson999]

Interesting request...way back when I was a student pilot, it was drilled into me that I should always have an abort point selected *ahead of time* on every take-off. If not off the ground by that point, abort the take-off. Sort of like computing the accelerate-stop distance the airlines do...ahead of time.

 

[KRviator]

I would be wary about requesting something like this.

An "accelerometer vs runway remaining" has been requested by the FAA, ATSB & NTSB as far back as the 70's IIRC and they still don't have one on the flight deck of the 787!Mind you, the airlines have only just discovered touch-screens this last year... ;D

We take off with airspeed, acceleration sensed/measured would be a physical sensation relative to movement over ground, so how would you reconcile the two? We already have the trend indicator on the ASI, but I can't recall actually using that all that much.

Something like this might be fine where ASDA's are borderline, but for most of us I think what we have is fine and I'd prefer the development time to go towards something like a wearable HUD (think GRT Vision) or PFD data overlaid on an external video, as from a FLIR camera. Or automatic envelope protection.

 

[Doug1]

Hi
KRviator

What I had in mind was a display showing airspeed acceleration, that is the rate of airspeed change per unit time.
This acceleration figure, on any given day will be affected by variables such as surface, headwind etc.
At any displayed acceleration, SV can easily calculate the time remaining until rotate speed is reached,
assuming that acceleration remained constant.

In parallel, you can calculate the ground speed acceleration based on GPS ground speed. At any calculated GS acceleration
SV can calculate the distance that will be travelled in the time to rotate IAS is reached as calculated above.

This distance is then compared to the take off distance remaining based on the entered typical takeoff distance.
Note that a complication is deciding when the takeoff roll has begun, so that the distance travelled so far can be zeroed.
This may be problematic. It would have to be automatic.

(An alternate would be not to show acceleration at all - just show required takeoff distance remaining to reach rotate IAS
as the takeoff roll proceeds, based on the calculation above. This might be even better!)

How easy this is to implement depends on the software design of SV. If the structure allowed easy addition of gauges to the EMS
maybe it is a goer, but, I agree that if the development time was excessive there may be better things to do.

Doug

 

[CGameProgrammer]

Personally I think acceleration would be almost useless as well as misleading because the speed required to fly varies based on your total weight (passengers, cargo, and fuel) as well as density altitude.

A more useful metric, that does not make assumptions, would be to indicate runway distance remaining. It already knows the runway lengths and elevation so it can easily calculate whether or not you're on a particular runway, and when you are it would be useful to indicate remaining distance. This could be useful when taking off and also when landing, if it can reasonably deduce when you're preparing to land on a runway.

 

[Dynon101]

Actual aircraft acceleration in Gs is a very useful indicator during takeoff performance.

The Dassault Falcon aircraft have them and it is most helpful during contaminated runway ops.

 

[ChiefPilot]

We already have the trend indicator on the ASI, but I can't recall actually using that all that much.

That's because it's been broken since at least v14 and maybe earlier. Dynon has either chosen to not fix it or is not capable of doing so.