We were waiting at Chandigarh Airport for our flight to Delhi. The aerial distance between the two cities is less than 250 km, and flights take about 30 to 40 minutes to cover the distance. My wife, who was travelling with me, saw a turboprop on the tarmac and remarked: “look at that small plane – does it even fly”. When I told her that that is going to be our aeroplane for this flight she seemed a bit worried. Then there is another colleague of mine who has never travelled on a turboprop aircraft and instead would prefer to travel by road.
The turboprop is probably the most unloved and most misunderstood aircraft. The look of a propeller makes one think that the aircraft is of a World War II vintage design. Nothing can be further from the truth.
What is the difference between the two aircraft types?
At an elementary level, both engine types – the Turbojet and Turboprop are identical except for the fact that a propeller replaces the fan in a jet. Both are, therefore, real jet engines. The difference is in the thurst produced by the engine – a propeller-driven engine will always produce less thrust than a fan-driven engine of almost equal size. The images of the actual aircraft of the right-hand side in the diagram make that fact even more apparent. These engines are not to be confused with piston-driven propeller engines.
Turboprops are Cool
I prefer a Turboprop to a Jet on a short-haul flight. Many pluses and no minuses. The seating is 2×2 single-aisle. It is a bonus if one gets a window-seat as the windows are large and the overhead wings do not spoil the view below. The crew has enough time to serve the passengers in the right manner rather than rushing through with your sandwich and coffee. These planes fly at a cruising altitude of around 15,000 feet – whereby one can still make out the roads, fields and other landmarks quite clearly. For a short-haul flight, the end to end time spent is the same. A few minutes faster in the air on a Jet doesn’t save you any time at all. The whirling and whining of the engines gives you the feeling of a real flight!
A Case Study: ATR 72-600 vs Airbus A320neo
Let us compare the performance of two top-rated aircraft – an Airbus A320neo (VT-ITR) and an ATR 72-600 (VT-IYO) of Indigo Airlines on a short-haul flight of Bangalore to Hyderabad, the distance between them being 245 nm. A flight by an ATR 72-600 takes just 20 minutes more than an A320neo.
The cruise altitude duration of an A320neo is only 14 minutes, which means the aircraft spent 35 minutes in climbing and descending. The short cruise duration also implies that much of the fuel is wasted in climbing to 31,000 feet. The fuel economy per seat of both aircraft are almost the same, but at full load (180 passengers in A320neo vs 78 in ATR 72-600) an A320neo will be marginally more fuel-efficient. However, if the load is lesser, an ATR 72-600 will become much more efficient.
Aviation Magazine says –
For short distances, turboprops are more fuel-efficient than jets. On the longer flights, the jet (turbofan) engines win the race. Turbofan engines perform best at high altitudes. At medium and low altitudes, the turboprops are more efficient engines. Since all flights start and end at low altitudes, the high altitude cruise segment needs to be long enough for the turbofan engine to offset it’s a disadvantage during start and landing.
The break-even point is somewhere between 300 and 500 nm.
As an ending note about other Turboprops or smaller regional jets like the Q-400, CRJ-700 and the Embraer E-170, the ATR 72 is the lesser of the two turboprops in performance but displays better fuel economy. For a typical Bengaluru-Hyderabad sector, which is 250 nm, the aircraft consumes approximately 770 kg of fuel. The Q-400 consumes close to 1,000 kilograms, the CRJ-700 consumes close to 1,200 kg, and the Embraer E-170 1,300 kg; all three aircraft carrying 78 passengers.
A Turboprop aircraft is best suited for short-haul trips, shorter runways and fewer passengers. Airlines that are using larger aircraft like A320’s or B737’s are losing on fuel efficiency and costs. In days to come mid-capacity turboprops are going to gain popularity.
Let us know your opinion on Turboprops in the comments section below.