Fuel Efficiency Characteristics of Regional AircraftAshish Gupta99D01003

Regional Aircraft

Aircraft with less then 100 seats.Turboprop and Regional Jets.

Example:TP: Bombardier Q300RJ: Bombardier CRJ200

Demand for Air-Travel:• 9.0% average growth rate since 1960.

• Growth of 4.5% per year over the last Decade.

• Estimated future worldwide growth at 5.0% till 2015.

Environmental:• Attributes 3.5% of total emissions.

• Aircraft emissions at altitude is potentially twice severe withrespect to climate changes compared to ground level emissions.

Importance of Regional Aircrafts:• Traffic flown by regional airlines grew almost 20% in 1999

• Expected annual growth of 7.4% during next decade

• Expanded hub-and-spoke operations

• Creation of new hub-bypass routes

• 7% of jet fuel use

• 40-50% of total departures

• 4% of domestic revenue passenger kilometers (RPK)

The Energy Efficiencies of Aircraft:• Specific energy usage (Eu)

Units of energy consumed per available seat kilometers (ASK)

• Specific energy intensity (EI)

Units of energy consumed per RPK

Eu is closely related to environmental performance of aircraft system.

• Load factor (α)

Ratio of Eu to EI

Turboprops are more efficient then Regional Jets

Regional aircrafts are less efficient then large aircrafts.

Technological Influences on Energy Usage:Three aircraft performance metrics• Engine efficiencies

Thrust Specific Fuel Consumption (TSFC)

• Structural efficiencies

Operation Empty Weight (OEW)

Maximum Take-Off Weight (MTOW)

• Aerodynamic efficiencies

Maximum Lift to Drag Ratio (L/D)

Cruise value of TSFC have improved by 25% since 1960 for both TPand RJ

Structural efficiencies of all aircraft have decreased between 10 - 25%

Aerodynamic efficiencies has improved by 15% for all aircraft

Using aircraft performance metrics the value of specific energy usage at cruise (Eu,cr) is estimated using:

Where:

• No distinct technological advantage which results in lower fuel consumption

• Difference in Eu and Eu,cr is caused by fuel consumption incurred during non-cruise portions of aircraft operations.

Influence of Operations on Energy Usage:Aircraft operations – airports served, stage lengths flown, and flight altitude – have significant impact on the Eu of regional aircraft.• Shorter stage length

• More time at airports taxing, idling, and maneuvering into gates

Ground Efficiencies (ηg):A useful efficiency metric for evaluating the amount of time aircraft

spend on the ground compared to in the air is the ratio of airborne hours to block hours

Airborne Efficiencies (ηa) :• Define as ratio of minimum flight hours to airborne hours.

• Minimum flight hours means time to cover stage length only by cruise.

• Captures the influence of others in-flight inefficiencies.

Total Impact of Operations on Energy Usage:The ground and airborne efficiencies together captures the

important operational characteristics of commercial aircraft and explains the difference between Eu and Eu,cr.

Influence of Load Factor:

• Load factor for large aircraft has improved by 50% for large aircrafts

• No distinct improvement in load factor for both TPs and RJs

• But load factor of RJs is always higher by 10 -30% from TPs

Cost Characteristics of Regional Aircraft:

Regional Aircraft Unit Cost:• Defined as the ratio of direct operating cost (DOC) to available seats kilometers (ASK)

• Regional Aircraft are 2-5 times more expensive to operate than large aircraft

• Using multivariable regression analysis the relationship for unit cost as a function of stage length (SL) and Eu was found

• 1/SL term represent the contribution of fixed cost to total cost

• Eu represent the cost of fuel and pilot wages

Higher the stage length lower the unit cost

Conclusions:• No distinct technological advantage that results in lower fuel consumption under optimal cruise conditions.

• Operational efficiencies has clear relation with fuel consumption

• Cost of operation depends upon the stage length

References:1. Babikian, R., Lukachako, S.P., Waitz, I.A., 2002. The historical fuel

efficiency characteristics of regional aircraft from technological, operational, and cost perspectives. Journal of Air Transport Management 8, 389-400.

2. Lee, J.J., 2000. Historical and future trends in aircraft performance, cost and emissions. MS Thesis, Massachusetts Institute of Technology, Cambridge.

3. Lee, J.J., Lukachko, S.P., Waitz, I.A., Schafer, A., 2001. Historical and future trends in aircraft performance, cost and emissions. Annual Review of Energy and the Environment 26, 167-200.

4. Dresner, M., Windle, R., Zhou, M., 2002. Regional jet services: supply and demand. Journal of Air Transport Management 8, 267-273.

5. Wu, C.L., Caves, R.E., 2000. Aircraft operational costs and turnaround efficiency at airports. Journal of Ait Management 6, 201-208.