## 272 Tradeoff studies

The outcome of the constraint analysis may be the selection of a different geometry for the aircraft than currently specified for the baseline configuration. Since it will be necessary to recalculate the baseline aircraft with these new values, it is worth considering other changes that might be beneficial to the design. For example, the wing aspect ratio may have been selected from arbitrary data from other aircraft. It would be appropriate to assess this decision as more detailed analysis of...

## 451 Conventional layouts Figure

This must be regarded as a strong candidate for our baseline aircraft configuration as it is a well-proven, low-risk option. The technical analysis is relatively straightforward and has a high confidence level in the accuracy of the results. Its main advantage is that it is similar to the competitor aircraft and thereby with airport existing facilities and operations. There are some drawbacks to choosing this layout. These relate to the geometrical difficulties of mounting a high-bypass engine...

## Manoeuvring

The best way to approach the manoeuvring analysis is by generating data matrices of altitude and aircraft speed. These provide the values for aircraft drag and engine thrust at the aircraft weight and load factor to be considered. Computer programs or spreadsheet applications are the best way to perform the calculations repeatedly for different flight cases. The specific excess power (SEP) is calculated at each point (height and speed) of the data matrix by the formula T thrust D drag W...

## 484 Wing geometry studies

To conduct a full and accurate analysis of the wing parameters (e.g. area and aspect ratio) would involve a full, multivariate optimisation method. As most of the design parameters are interconnected this would be a complex process. At this early stage in the design process and with limited resource and time available, it is not possible to undertake such a comprehensive study. Some simplifying assumptions are necessary to enable a sensitivity study to be done. For example, we may assume that...

## 87 Constraint analysis

As the initial mass (weight) and aerodynamic estimates have now been made, it is possible to conduct a constraint analysis to determine if the original choice of thrust and wing loading values are reasonable. As these were derived from data on other aircraft, it is likely that a better selection can improve the design. This process will also indicate which of the constraints on the problem are most critical. The equation below, as developed from the specific excess power relationship in Chapter...

## 765 Structural details

There is an essential difference in structural design considerations for aircraft and cars. For aircraft, low weight with strength is paramount, while automobile designers need to add a focus on structural stiffness to improve handling and suspension performance. For this project the structure was designed to meet both general aviation aircraft and automobile requirements (FAR 23 and US National Highway Transportation Safety Advisory respectively). The aircraft loads and their distributions...

## 661 Initial mass estimations

As the aircraft propulsion system does not use conventional fuels, and since the flight duration of the race is short compared with non-racing aircraft, conventional methods of predicting take-off mass are not appropriate. In this case, it is necessary to make the initial calculations using known data to validate an acceptable estimation. Data from the two closest existing aircraft to our designs, namely the Nemesis racer and the FFT Speed Canard, will be used to verify the estimation formula....

## 622 History of Formula 1 racing further reference can be found on the Formula 1 web site1

Prior to 1945, racing aircraft were mostly original designs specifically aimed at racing. They were unique creations that often advanced the field of aeronautics. Innovative designers of air racers consistently produced aircraft that outperformed the best military aircraft of the day. In the early days, these aircraft led to the development of monoplane wing layouts and introduced materials and construction methods that were lighter and more reliable. After World War II, there was a surplus of...

## 662 Initial aerodynamic considerations

Aircraft speed is one of the most significant factors in racing. Therefore, the main aerodynamic analysis for racing aircraft focuses on the reduction of drag. The layout details of the two aircraft will affect the aerodynamic calculations. The pusher propeller configuration will reduce the size, and therefore the wetted area, of the fuselage. The clean flow conditions over the nose will help to maintain laminar conditions over the forward fuselage profile. The smooth contours on the front...

## Mission analysis

The mission analysis allows us to estimate the fuel requirements. The project brief specifies three different mission profiles. At this stage, it is not obvious which one of these will be most critical, therefore each will be analysed to determine the required fuel. The calculations use the weight fractions suggested in Raymer's book1 for the less significant segments of the missions. Using the aerodynamic analysis described earlier it is possible to determine the lift drag ratio variation with...

## 761 Aerodynamic estimates

This design incorporated a unique combination of aerodynamic concepts including a telescoping outboard wing. These made the analysis of vehicle performance a challenging prospect. The aerodynamic examination needed to consider both in-flight and highway modes. These operating conditions presented contradicting aerodynamic requirements. The analysis was described in detail in the final project report.3 A summary of the main findings is given below. The analysis of the in-flight aerodynamics...

## 463 Wing geometry

The recommended wing loading is 450 kg sq. m, hence Wing gross area (S) 80 923 450 180 sq. m (1935 sq. ft) Selecting a high aspect ratio (AR) will lower induced drag in cruise and save fuel. A value of 10 is to be used. The choice of aspect ratio will need to be reviewed in a trade-off study later in the design process. Using the wing area and aspect ratio we can determine Wing span (b) (AR x S)0 5 42.4 m (135 ft) Mean chord (cm) (b AR)) 4.24 m (13.5 ft) Selecting a taper ratio of 0.3 gives...

## 762 Powerplant selection

Propulsion represented a unique problem for this design since the selected engine must provide power for both airborne and highway use. Alternatively, two separate engines could be used. Based on the drag calculations above with a cruise at 150 kt (77.2 m s) at 3000 m (9843 ft) altitude, and an estimated maximum gross weight (maximum take-off mass) of 3308 lb (1500 kg), it was found that a cruise engine power of 207 hp (155 kW) was required. The use of two engines was considered, one to power...

## Normal takeoff distances

The take-off distance is the sum of the ground distance (sg) and the rotation distance (sr ). The ground distance is that travelled along the runway up to the point at which the rotation speed is reached. The rotation distance is a nominal distance to account for the rotation of the aircraft to achieve the initial lift-off manoeuvre, prior to the climb from the runway. Take-off speed (VTO) is defined as that reached at the point that the aircraft leaves the runway. To avoid inadvertent...

## Technical books in alphabetical order

J., Bertin, J. J., Whitford, R., Introduction to Aeronautics A Design Perspective, AIAA Education Series, 1997, ISBN 1 56347 250 3 A book based on the lecture courses for new recruits to the US Air Force Academy and as such is a good introductory text. The case studies (Wright Flyer, DC-3, and F-16) are more concerned with historical development than as examples of technical analysis. The sections on 'Performance and constant analysis' and 'Sizing' are worth some...

## 271 Constraint analysis

From our earlier work on understanding the problem section 2.1.3 we identified several constraints that must be satisfied by the aircraft design. Many of the specified constraints are related to the performance of the aircraft for example, minimum speeds or climb gradients . The requirement will be written in the form At a specified aircraft flight condition and configuration, the aircraft must demonstrate a performance no less than a specified value e.g. climb gradient better than 0.024 with...