21st Jul 2009, 13:55
What's the best technique for the quickest time around a closed course like Reno ?
1. The shortest possible route around the course pulling limit / max g turns around the pylons ?
2. A slightly wider route requiring less G in turns reducing induced drag losses and possibly a higher average indicated airspeed ?
Practical experience and theoretical discussion all welcomed !
21st Jul 2009, 19:29
Starter for 10
It depends what the specific performance of the aircraft is and where the "corner point" is on the flight envelope.
I would have thought that ideally you would want to fly to the corner point which is where you get the biggest rate of change of heading for a given g. Slower then the corner point you are limited on AOA and head towards the stall so have to back off the turn rate, faster than the corner point you are structurally limited (max g) and so your turning circle get bigger and bigger as speed increases.
There are huge numbers of factors though such as excess performance at a given flight condition (which will define how quickly you can accelerate the aircraft after a turn). If your acceleration is poor, you might want to keep more speed on and take the hit on the turn rate.
8th Aug 2009, 17:52
Bit late catching up on this but here goes-spoken/written with the authority of racing in F1,there,I`ve said it(aeroplanes..) over about 8 years,and won a few `pots` too.. It all depends......
on the circuit,shape,length,level,obstructions/pylon visibility,runway length/width,wind velocity,scatter pylon..
on the aircraft-fixed pitch props, aerodynamics-(wing-shape,aspect ratio),cleanliness(drag reduction);
on the pilot-experience on type,smoothness of flying, situational awareness, psychology(low cunning !)
on the other pilots- ditto above..
By F1 I mean aircraft that were designed to a minimum formula,ie wing area 66 sq ft, min wt xxlbs?, 1 pilot,fixed gear,engine nominal hp 100,ie 0-200/c-90,fixed pitch prop,no super/turbo charging,fully stressed for aeros,+/-6 G min.
I`ll elaborate later...
28th Aug 2009, 05:09
As sycamore has said above, there are a huge amount of variables that need to be taken into consideration.
It would probably take thousands of pages worth of posts to discuss "unlimited class" while a "spec. class" would be a lot easier.....but you still have lots of plane to plane variation.
Aseanaero has opened up a topic that cannot be answered easily.
There is a forum when many of the racers communicate.
Air Racin' - Aviation Airshow Air Race Photography Discussion (http://www.aafo.com/hangartalk/forumdisplay.php?f=2)
28th Aug 2009, 19:53
I had a discussion with some Reno racers and the consensus is that the smoothest way around (taking into account you can also climb and dive slightly in turns) without sustaining a lot of really high G is the quickest way around a closed course.
It also depends on the aircraft type , some accelerate better than others and others don't bleed off lots of speed in turns.
15th Sep 2009, 23:04
There is the "excess energy" concept used in assessing fighter manuvering capability - I suspect that this may be of some value in "pylon polishing" (Benny Howard's term).
Genghis the Engineer
16th Sep 2009, 08:58
Found here (http://www.raes.org.uk/aero_journal.asp)
Trajectory optimisation of an aerobatic air race
Volume 113, Number 1139 (Click to browse/purchase by issue)
H. van der Plas and H. G. Visser
This paper deals with the synthesis of optimal trajectories for aerobatic air races. A typical example of an air race event is the Red Bull Air Race World Series, where high-performance aerobatic aircraft fly a prescribed slalom course consisting of specially designed inflatable pylons, known as Ďair gatesí, in the fastest possible time. The trajectory that we seek to optimise is based on such a course. The air race problem is formulated as a minimum-time optimal control problem and solved in open-loop form using a direct numerical multi-phase trajectory optimisation approach based on collocation and non-linear programming. The multiphase feature of the employed collocation algorithm is used to enable a Receding-Horizon optimisation approach, in which only a limited number of manoeuvres in sequence is considered. It is shown that the Receding-Horizon control approach provides a near-optimal solution at a significantly reduced computational cost relative to trajectory optimisation over the entire course. To avoid the path inclination singularity in the equations of motion based on Euler angles, a point-mass model formulation is used that is based on quaternions. Numerical results are presented for an Extra 300S, a purpose-designed aerobatic aircraft.
I've read the paper and wasn't fantastically impressed that it answers all the questions. My specific criticisms are that:
- It takes its data for aircraft characteristics from Microsoft Flight Sim, there are better sources!
- There doesn't seem to have been any attempt to validate their analysis/simulation by getting some real air race data.
- There doesn't seem to be any consideration of the effects of induced drag in a turn.
- It ignores the effects of wind.
But, it's a start at the problem.
16th Sep 2009, 11:02
Genghis wins the turkey :ok: