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Ticket #815 (assigned enhancement)
Auto-bug integrator
| Reported by: | hjr | Owned by: | jwharington |
|---|---|---|---|
| Priority: | normal | Milestone: | XCSoar Wishlist |
| Component: | Other | Version: | unspecified |
| Keywords: | polar and bugs | Cc: |
Description
I wish to replace the bug based polar performance reduction to some more convenient and potentially more (often) realistic polar.
This because of my experience is:
- I usually forget to set the performance reduction "in time".
- I normally know the bug expectations for the day, conditions are predictable
Thus the xc speed could be better supported. A solution would affect both sides of the system, 1) the bug setting and 2) the polar math on that.
To 1) an algorithm replaces manual settings while flying, the "auto" way:
- Flight setup has a setup for the bugginess of the day: [none, few, medium, alot]
- A Bug-wiper button resets the auto algo to restart to a clean wing.
- Maybe some functionality could cover the rain use case, but I am not sure what value it has.
The algo integrates for the circling time and the time spent below 300m AGL bugs according the bugginess of the day. Best case this would map the integrated time through some log characteristic to the known percentage value, so that at the end of the day a maximum achievable pollution is reached (no wipers so far).
Point 2) is certainly a bit more of research. I see that the polar scaling does not influence v min, but bugs do. So there should be a better model to get the bugs mapped into the polar.
Change History
comment:2 Changed 16 months ago by Turbo
- Owner set to jwharington
- Status changed from new to assigned
comment:3 Changed 14 months ago by jwharington
Whilst bugs accumulation (bugs per sq meter per hour) may be expected to be linear, the effect on performance is not --- and this nonlinear relation of bugs per sq meter to % degradation will depend on the airfoil type. Very old airfoils (pre 1970s) that were not designed for laminar flow will have reduced bug dependency, and new airfoils (post 1990) are designed to be more bug tolerant.
Without reasonable data for this, I expect that integrating bug accumulation will be futile.
Could someone please look into this, and see if there is any data available that could help us?
I am pushing this to 6.2 milestone since I dont want to implement it until it will be reasonable.
I would actually support some kind of automatic adjustment of the hypothetical performance from the polar to arrive at some achieved performance.
However there are other reasons despite bugs for wanting an adjustment for this value, i.e. I usually set the clean value to "90%" to adjust for my less than perfect flying which not really correlates with altitude and also not (a lot) with time. Also the effect of bugs depends significantly on the airfoil of the plane, e.g. a LS1 will have a significant performance drop for relatively few bugs while a ASK13 will be nearly unaffected. In other words: A single "expected bugginess" value will probably not be sufficient.