1. Regional Aircraft/Corporate-General Aviation
Sudarshan Kumar
Associate Professor
Aerospace Engineering Department
IIT Bombay, India

2. Regional airline
A regional airline is a small airline designed to fly up to 100 passengers on short-haul flights,
Feeding larger carriers' hubs from small markets.
This class of airliners are typically flown by the regional airlines
that are either contracted
subsidiaries of the larger airlines.

3. General features
Regional aircrafts are % less fuel efficient than their larger, narrow and wide body counterparts employed for long range
Regional jets are % less fuel efficient than turboprops
The difference in efficiency largely depends on the differences in operation rather than on technology.
Operating costs per passenger are 2- 6 times higher for regional transport

4. Why regional transport

5. History To keep these short routes economical,
Airlines were generally unwilling to spend large amounts of money on new aircraft;
Used available aircrafts
Slowly new aircrafts models emerged,
In the post-war era
Douglas DC-3s,
De Havilland Dragon Rapider
Convair 440,
Douglas DC-6
Vickers Viscount

7. Duglas DC-3 Developed in 1935 Fixed wing propeller driven aircraft
More than planes were built and flown
Early 1950s’ turboprop conversions
It is still being operated by some revenue and cargo companies
Technical specifications:
1200 bhp radial piston engines (PT6 engine variants)
Later P&W engines used with 433 – 1447 kW shaft power
Rolls Royce engines (RB 53 Dart) 1800 bhp shaft power

9. Bombardier Dash 8 Two engines, medium range turboprop airliner
Over 1000 planes have been ordered
STOL performance
Improved cruise performance
Low operational costs
Engine (P&W – PW100)
Seating capacity 39 – 80 with a range of engines
Can operate from smaller runways (910 m)

10. Regional jet

11. Regional jet Although more expensive that the turboprop
Favored for routed not suitable for turboprops
Lower maintenance costs of turbojet engines
30% more fuel consumption

12. According to Bombardier marketing, the aircraft breaks even
For about 1/3rd of its seats filled
Or 1/4 with more closely spaced seats
Making it particularly attractive on routes with varying passenger numbers
For example, Island Air in Hawaii calculated that the use of a 50-seat Regional Jet would break even at 45 passenger seats compared to the Q400's seats (~55% breakeven load factor).
For most short-haul routes (< 500 km),
time spent on taxiing,
takeoff
Landing
This eliminates a competing jet's speed advantage.
Q400's 414 mph (667 km/h) cruise speed approaches jet speeds,
Short-haul airlines can easily replace a regional jet with a Q400 without changing their gate-to-gate schedules.
Bombardier has singled out the Q400 for more aggressive marketing,
Competes in the 90-seat market range
Bombardier commercial aircraft president Gary Scott has affirmed that
By we are planning to offer a stretched version of the Q400 turboprop.

13. Indian regional jet

14. Indian regional jet

15. Indian regional jet (IRJ)
Jointly proposed by NAL and HAL in 2007
70 – 100 seater aircraft
Common platform for turbo prop and turbo fan engines
95 % of the airframe and other systems same
The aircraft claimed to offer
25% lower acquisition costs
25% lower operating costs
50% lower maintenance costs than existing turboprop regional aircraft.
Specifications:
Range: 2,500 km, Runway length: 900m
Aircraft length: 28.6m Wing-span: 29.4m
Service ceiling: 30,000 ft, Cruising speed: 300kt,
Noise level to meet Stage 4 criteria. Composite airframe
60% lower emissions Ability to operate from ill equipped airfields
Cabin dimensions: Length m and height m.
Cargo version to have 25 m3 volume.
Indigenous fly-by-wire control system, Open distributed modular avionics,
Automatic dependence surveillance Broadcast navigation capabilities, and advanced displays

16. ATR-72

17. ATR 72 ATR 72 was developed from the ATR 42
To increase the seating capacity (48 to 78) by stretching the fuselage by 4.5 metres (15 ft)
Increasing the wingspan
Adding more powerful engines
Increasing fuel capacity by approximately 10 percent.
The 72 was announced in 1986,[2] and made its maiden flight on 27 October 1988.
One year after that, Finnair became the first airline to put the plane into service
Since then, at least 408 ATR 72s have been delivered worldwide with orders pending on at least 28 more.
Design
Passengers are boarded using the rear door (quite rare)
The ATR aircraft does not have an auxiliary power unit (APU)
"Hotel Mode") that stops the propeller on the #2 (right) engine, allowing the turbine to run and provide air and power to the aircraft without the propeller spinning.
General characteristics
Crew: 2
Capacity: 68 to 74 passengers
Length: 27.17 m (89 ft 2 in) Wingspan: 27.05 m (88 ft 9 in)
Height: 7.65 m (25 ft 1 in) Wing area: 61.00 m2 (656.6 sq ft)
Aspect ratio: 12.0:1 Empty weight: 12,950 kg (28,550 lb)
Max takeoff weight: 22,500 kg (49,604 lb) Powerplant: 2 × Pratt & Whitney PW127F turboprops, 1,846 kW each
Performance
Cruise speed: 511 km/h Range: 1,324 km
Service ceiling: 7,620 m Takeoff Run at MTOW: 1,165 m (3,822 ft)

18. Embraer jet

19. Embraer- ERJ family
The aircraft ERJ family is powered by two turbofan engines (Rolls-Royce AE 3007)
Thrust: 30 – 42 kN
Pressure ratio 20: 1
Turbine inlet temperature: 1300 K
Thrust to weight ration : 5: 1
Capacity 37 – 122 passengers
Sold around 1800 jets in last 15 years
Service ceiling: m
Cruise speed: kmph
Range: km
The ERJ E family employs GE CF34- 8E/10E engine series
Thrust: 63 – 89 kN thrust
Range – km
Cruise speed: 890 kmph
passengers

20. Energy efficiency and load factor
EI = Energy intensity – energy consumed per ASK (available seat per km)
EU = Energy usage- energy required per km
a = load factor
EI– energy consumed per ASK
Constant for all the aircrafts
EU = Varies from one aircraft to another
Depends on
Technological advancement
Size
Mission
Propulsion system type
Operational efficiencies

21. EU of regional aircraft and their yearly average

22. EU of regional aircraft and their yearly average
EU of regional jets has improved with an annual rate of about 2 % per year
EU of turboprops has improved by ~1.5 % per year.
Although regional jets are ~ 50 % less efficient than turboprops
But the technological advancement has helped in catching up with turboprops.
Reason: More investment into improving the fuel efficiency of jet engines.
Long range aircrafts most lucrative field
Technology developed for those engines is simply transferred to regional jets
Not much investment into the turboprops because of their limited application
regional transport
lower speed as compared to regional jets

23. EU comparison of large and regional aircrafts
Drastic decrease in the E indicates technological advancement due to demand for long distance travel

24. Specific fuel consumption of Engines

25. Specific fuel consumption
TSFC is 10-25% higher for regional jet as compared to large jet because of delay in implementation of new technology to regional jets
For smaller size the gap remains as efficiency of a system can not be improved when size of the engine is reduced …e.g. regional transportation
Due to limitation of engine size, smaller jet engines employ smaller lower pressure ratio engine and hence reduced efficiency.
Hence lesser compressor stages and less efficient than centrifugal compressors
Turboprops are % more efficient than regional jets.
Turboprops deliver 85% of the total thrust from propellers.
Due to their ability to accelerate large amount of air at small speeds.
Advantageous for takeoff, climb operation and low speed operation

26. Structural efficiencies
1% reduction in the gross weight reduces the specific fuel consumption by 0.25 – 0.75%.
Despite availability of best materials i.e. composites, most of the aircrafts contains ~ 97% metallic with very few composite components
Reduction in the component weight is offset by integration of new passenger facilities i.e. personal entrainment systems
For smaller engines, thrust to weight ratios are typical lower
Turboprops are quite poor because of high weight of engine components (e.g. Speed reduction gearbox; mechanisms to alter propeller pitch)

27. Trends in structural efficiency

28. Aerodynamic efficiencies

29. Energy usage for various aircrafts

30. Energy usage
EU for large aircrafts is approximately 1.6 times to that of EU,CR
For regional aircrafts, the number is app. 2.6
For turboprops, it is approximately 2.5 times

31. Operational sequence influence

32. Ground Efficiencies

33. Airborne efficiency

34. Energy usage Vs ground and airborne efficiencies

35. Operating costs

36. Pilot salaries and fuel costs
Pilot salaries (% of total cost) Fuel costs (% of total cost)

37. Operational cost Vs Stage length

38. Regional Daily flights distribution in 2002

39. Comparison of fuel consumption
Turboprop

40. Propulsive efficiency

41. Turboprops and Turbofans

42. Why regional transport
For regional transport
Many hubs located around the many centers
Delhi, Mumbai, Bangalore, Chennai, Hyderabad
Distance ~ 600 km
Importance of connectivity

43. Conclusions
Regional aircrafts have value of energy use times greater than larger aircraft
The difference is due to operational sequence rather than technological sophistication
Regional aircraft fly short lengths and spend large fraction of time in climbing to altitude than cruise.
Turboprops have inherent advantage than regional jet as they can cruise efficiently at a much lower altitude than regional jets and at much lower speed.
Fuel costs are
~ 26% for larger aircrafts
~ 20% for regional jets
~ 13% for turboprops
Regional jets appear to be as good as turboprops because of their higher load factors.
If strategies are evolved to increase the load factors in Turboprops, they are the best option of economical transport at regional levels.

44. References
Smirti and Hansen, “The effect of fuel prices on comparative aircraft costs,” National center of Excellence for Aviation Operations Research
Babikian et al., “The historical fuel efficiency characteristics of regional aircraft from technological, operational, and cost perspectives,” Journal of air transportation management, 8(6) 2002,
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