The VEMD/FLI an idiots "substitute Pilot's" guide for the AS350B3
LNRalph - you would need to establish the max continuous. max contingency and any time-limited figures (ie 5min take-off) for the various parameters and use these as your benchmarks. The FLI is what it suggests, a first limit, whether that be Tq, Ng, T4 or bananas and that first limit will be either max continuous or max contingency depending on the manufacturers limits. You just have to juggle the numbers so your software recognises which iit is hitting first. I expect the yellow band will be max continuous and the red line will be max contingency.
Join Date: Mar 2009
Location: Sandefjord
Age: 39
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
I know the idea behind the FLI value (and I am a pilot myself), but figuring out how the limits are calculated is the tricky part. I came up with a basic interpretation, which seems to work pretty well. The FLI value for T4 and Ng go up exponential when they come up to their limit, I have to narrow that band a bit more maybe. Here's a video of the current result.
but figuring out how the limits are calculated is the tricky part
Join Date: Mar 2009
Location: Sandefjord
Age: 39
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Finding the limits is indeed not the problem 
It is figuring out what FLI value they represent, probably also combinations form a certain value. I'm afraid that no one knows except for Thales and Airbus.
It is figuring out what FLI value they represent, probably also combinations form a certain value. I'm afraid that no one knows except for Thales and Airbus.
but you have an amber and a red line on your FLI - surely the start of the amber section would be max continuous and the red line would be max contingency with anything above that being time-limited transients.
On your illustration you seem to have amber from 9.5 to 10 FLI with another red dot (transient) just under 11 FLI. I suspect Tq and Ng are probably close to linear up to the limits whilst maybe T4 varies a bit more with airflow.
On your illustration you seem to have amber from 9.5 to 10 FLI with another red dot (transient) just under 11 FLI. I suspect Tq and Ng are probably close to linear up to the limits whilst maybe T4 varies a bit more with airflow.
Join Date: Mar 2009
Location: Sandefjord
Age: 39
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Ng is not linear. It can be at 80% with an FLI value of 2. The torque seems to be indeed linear.
The FLI value for both Ng and T4 rise exponentially close to their limits. I've made a guess as to where this starts, but it seems to work quite alright. The real thing is probably way more complex.
The FLI value for both Ng and T4 rise exponentially close to their limits. I've made a guess as to where this starts, but it seems to work quite alright. The real thing is probably way more complex.
Ng is not linear. It can be at 80% with an FLI value of 2. The torque seems to be indeed linear.
The FLI value for both Ng and T4 rise exponentially close to their limits. I've made a guess as to where this starts, but it seems to work quite alright. The real thing is probably way more complex.
The FLI value for both Ng and T4 rise exponentially close to their limits. I've made a guess as to where this starts, but it seems to work quite alright. The real thing is probably way more complex.
Join Date: Feb 2009
Location: A nice place
Posts: 160
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by [email protected]
LNRalph - you would need to establish the max continuous. max contingency and any time-limited figures (ie 5min take-off) for the various parameters and use these as your benchmarks. The FLI is what it suggests, a first limit, whether that be Tq, Ng, T4 or bananas and that first limit will be either max continuous or max contingency depending on the manufacturers limits. You just have to juggle the numbers so your software recognises which iit is hitting first. I expect the yellow band will be max continuous and the red line will be max contingency.
Join Date: Mar 2009
Location: Sandefjord
Age: 39
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Haha exactly There's some rough information to go with, but the (exact) calculation/algorithm stays secret. Also delta Ng, sounds easy, but over what time period? 100 milliseconds? 1 second? 10...? It will stay a big mystery imI afraid, all we can do is guess and try to come as close as possible.
There's some rough information to go with, but the (exact) calculation/algorithm stays secret. Also delta Ng, sounds easy, but over what time period? 100 milliseconds? 1 second? 10...? It will stay a big mystery imI afraid, all we can do is guess and try to come as close as possible.
How about taking flight idle's ng , Tq, and t4 right before takoff as FLI=0 (or 1 if you prefer)
and interpolate between this and max. continous?
The interesing part is the gradual reduction of the margin to "max. allowed FLI" while operating in the higher than continuous area,
especially when having "used" 4 mins. of some "max 5. mins limit" a reduction of power demand to below max. continuous for 3 seconds probably should not allow another 5 mins. of over max. continous power.
That is you need to model a "cool off" phase for each transient limit and all possible combinations thereof
which only when fully achieved enables another run of the "5 mins. limit",
but when that cool off phase was shorted the "5 mins." limit would become a "2 mins. limit"
P.
and interpolate between this and max. continous?
The interesing part is the gradual reduction of the margin to "max. allowed FLI" while operating in the higher than continuous area,
especially when having "used" 4 mins. of some "max 5. mins limit" a reduction of power demand to below max. continuous for 3 seconds probably should not allow another 5 mins. of over max. continous power.
That is you need to model a "cool off" phase for each transient limit and all possible combinations thereof
which only when fully achieved enables another run of the "5 mins. limit",
but when that cool off phase was shorted the "5 mins." limit would become a "2 mins. limit"
P.
