Manoeuvres

The manoeuvres that are used in aerobatic competitions are split into two parts; manoeuvres performed in the RBAR in Section \ref{sec:man_RBAR} and other manoeuvres often used in other competitions in Section \ref{sec:man_others}.

RBAR

\label{sec:man_RBAR}

Every RBAR has a different track, but the tracks are similar when it comes to the manoeuvres that are performed. In Figures \ref{fig:track_abu} and \ref{fig:track_las} the race profiles of the 2015 Abu Dhabi and the 2014 Las Vegas race are shown, it shows the different manoeuvres that the aircraft go through. Figures \ref{fig:track_abu2} and \ref{fig:track_las2} shows a schematic picture of the racetracks. It can be seen from the manoeuvre graphs that the 2015 Abu Dhabi and the 2014 Las Vegas race use similar manoeuvres, this is the case for all (recent) RBARs.

0.45

\label{fig:track_abu}

0.5

\label{fig:track_abu2}

0.45

\label{fig:track_las}

0.54

\label{fig:track_las2}

This section will discuss the main manoeuvres that are performed to fly through the gates that are used during a race. It will give insight on the needed performance to be able to compete with the current aircraft in the RBAR, but it will also discuss the impact that a lesser or better performance in a certain aspect will have on the manoeuvres.

Level Flight

When going through the Start/Finish Gate or through one of the Level Gates the aircraft has to maintain level flight, its bank angle is limited between \(\pm\,10\,\degree\) \cite{RB-PartA}. Flying level is something any (working) aircraft will do, but for the RBAR it is important that the aircraft can do this very fast. The aircraft currently participating in RBARs have a maximum speed (\(V_{max}\)) of \(230-240\,knts\) \cite{RB-Planes}, however the RBAR regulations allow a Start-Gate-speed of only \(200\,knts\) \cite{RB-PartA}. After the starting gate the aircraft generally slows down as it will start to roll, pitch and yaw, which means a loss of kinetic energy, the maximum speed during the race is therefore quite close to the starting gate speed.

For the aircraft to be competitive its maximum speed should be close to that of its competitors and it should be able to accelerate very fast. It could still race the track if a lower maximum speed is achieved but it would not meet the track times of its fossil-fueled competitors and could only be competitive in its own racing category.

Slalom/Chicane

Every RBAR has a chicane through which the pilot should slalom. The regulations allow the pilot to fly past these pylons in any bank angle so either in level flight, in a knife edge manoeuvre or somewhere in between \cite{RB-PartA}. Currently the aircraft participating in the RBARs perform this manoeuvre by rolling followed by pitching up, this allows the fastest slalom manoeuvre. For a good performance in the slalom it is therefore important to have high roll and pitch rates, this allows the pilot to perform the slalom the fastest. Currently aircraft in the RBAR have a maximum roll rate (\(p_{max}\)) of \(420-440\,\degree/sec\).

If the E-SPARC can not reach these values its performance through the chicane pylons will be less resulting in a higher track time. When the rates are substantially lower the aircraft could have trouble going through the pylons, this can be a problem as this means that the RBAR tracks should be changed for the new electric category.

Manoeuvres between gates

To get from one gate to another the pilot has to perform a high G turn. The pilot chooses to go for a high or low turn depending on the race strategy. However, the design should enable the high G turn with an airspeed loss as low as possible.

Other Competitions

\label{sec:man_others} Besides the manoeuvres used in the RBAR there are manoeuvres which are only used for aerobatic competitions. In Chapter \ref{cha:market} it was explained that the target for the design was not only to compete in RBARs but also in other aerobatic competitions. These competitions can have different manoeuvres and should therefore be considered in the final design as well. The design will be optimized for the RBAR but should be able to safely do all the manoeuvres listed below:

• Spin During a spin the pilot intentionally lets one side of the wing stall, which causes the aircraft to spin around the yaw-axis in a corkscrew motion. It can be difficult to recover from a spin if the CG is placed extremely far aft, it is therefore important to balance the CG so that a recoverable spin can be entered \cite{stowell2007light}.

• Loop When an aircraft makes a loop (pitch through 360) it needs to be able to fly at relatively high angles of attack.

• Aerobatic Steep Turn An aerobatic steep turn is a turn with at least 60 bank angle. The main effect of a steep turn is that the airplane needs to withhold high g-forces, this should however not be a problem as the load-factor during most aerobatic races is much lower than the 10g the aircraft is required to withstand in an RBAR.

• Half Cuban Eight & Immelman & Goldfish These manoeuvres consist of a half loop and a half roll, in different orders. During this manoeuvre the same properties are required for a loop. This means that the aircraft should be able to have a high roll rate and be able to generate high lift forces to pull you into the loop.

• Wedge During the Wedge the aircraft climbs in a 45 line. It then needs to fly straight down and make sharp turn in order to fly horizontal. These manoeuvres require the aircraft to be able to conduct steep climbs and have a high roll rate.

• Point roll The goal of a point roll is to hold a certain angle during a roll. In order to do this the aircraft must be able to fly stable with a large roll angle.

• (Negative) Snap Roll Is a very fast roll caused by changing the pitch and the yaw very rapidly. The nose then moves rapidly up. For this manoeuvre the aircraft should have a high pitch and yaw rate.

• Rolling Turn For this manoeuvre the aircraft rolls and makes a turn. Here it also required that the aircraft remains stable while conducting a roll.

Depending on the chosen configuration, the following manoeuvres might be difficult or dangerous to complete.

• Hammerhead When conducting this manoeuvre the airplane is operating near stall conditions. It first climbs until it nearly stops and then rotates in yaw direction and flies straight down. For such a manoeuvre the airplane must have good stall characteristics and a relatively high yaw rate. This high yaw rate was not needed for the RBAR manoeuvres and is therefore an important characteristic that should be added if the aircraft will be used in other aerobatic competitions.

• Inverted Flight During an inverted flight it is desirable to still create lift and have the same characteristics, when the airplane is not inverted.

• Tail Slide In this manoeuvre the aircraft first flies vertical up until it nearly stops and then slides back. The pilot needs to turn the aircraft nose down and fly vertical down. Just as for the Hammerhead the aircraft must have good stall characteristics.

From the mentioned manoeuvres above it becomes clear that two new important characteristics are added that are not of main priority in the RBAR. The aircraft needs good stall characteristics and a high yaw rate to perform well in aerobatic competitions. To have a high yaw rate the aircraft will need a larger rudder than it would when just competing in RBARs alone, resulting in more drag. Since in a canard aircraft the canard stalls before the main wing a canard might run into trouble performing the italic manoeuvres in Table \ref{tab:manoeuvrability}. If the main wing of a canard aircraft does stall the behavior can be unpredictable which is unsafe.

\label{tab:manoeuvrability}