ENL / dB thresholds

[John Wood]

Hi there, does anyone know if there is an official decibel threshold
when recording Eng. Noise Levels for a competition at which the engine
is official considered "On"?

Thanks in advance for any information

[5Z]

>From the GNSS tech spec on the FAI website:

2.11.1 Engine Noise Level (ENL) systems. These systems record a
three-number ENL value with each fix.
They must be capable of utilising all of the whole numbers between 000
and 999. ENL is the preferred method
for recording MoP operation, because no wiring external to the FR is
needed, nor any special mounting of the
FR in the cockpit, nor, for IGC-approved ENL systems, is a specific
engine-run needed on each flight to
"prove" the system. However, in design, careful processing of the raw
noise signal is required (frequency
filtering and weighting) so that a MoP developing forward thrust always
gives a characteristically high ENL
value, whereas ENL values associated with normal gliding flight, are
significantly lower, including
aerodynamically noisy areas of flight such as high speed and flight
with canopy panels open under sideslip
conditions. (AL3)


There's a lot more involved than a simple sound volume measurement.

-Tom

[John Wood]

Thanks for the information.

5Z wrote:
>>From the GNSS tech spec on the FAI website:
>
> 2.11.1 Engine Noise Level (ENL) systems. These systems record a
> three-number ENL value with each fix.
> They must be capable of utilising all of the whole numbers between 000
> and 999. ENL is the preferred method
> for recording MoP operation, because no wiring external to the FR is
> needed, nor any special mounting of the
> FR in the cockpit, nor, for IGC-approved ENL systems, is a specific
> engine-run needed on each flight to
> "prove" the system. However, in design, careful processing of the raw
> noise signal is required (frequency
> filtering and weighting) so that a MoP developing forward thrust always
> gives a characteristically high ENL
> value, whereas ENL values associated with normal gliding flight, are
> significantly lower, including
> aerodynamically noisy areas of flight such as high speed and flight
> with canopy panels open under sideslip
> conditions. (AL3)
>
>
> There's a lot more involved than a simple sound volume measurement.
>
> -Tom
>

[Mottley]

John Wood wrote:
> Hi there, does anyone know if there is an official decibel threshold
> when recording Eng. Noise Levels for a competition at which the
engine
> is official considered "On"?
>
> Thanks in advance for any information

Make sure that your rules state that engines must be run before a
competition flight or in the case of Turbos before the Start in order
to get an engine trace for comparison of the ENL level with later
traces.

Regards
Bruno