I tried to find the visual differences between the ATR42 and the ATR72. I downloaded some images from Google but I can't find any. Would you help me?
The ATR72 is quite a bit longer than the ATR42, and has several more windows to allow for more passengers.
According to Wikipedia:
The ATR 72 was developed from the ATR 42 in order to increase the maximum seating capacity (from 48 to 78) by stretching the fuselage by 4.5 metres (15 ft), increasing the wingspan, adding more powerful engines, and increasing fuel capacity by approximately 10 percent.
So it's longer, and has larger wingspan. The stronger engines and larger fuel tanks can't be seen from the outside.
There are a lot of technical differences between the two aircrafts. In addition to fuselage length and wing span, like ATR 72 has three cameras in forward cargo area and near cockpit door + its display screens inside cockpit, antennas outside the fugelage are different, ATR 72 navigation lights are LEDs, where as ATR 42 nav lights are normal bulbs. Similarly the cabin lights of 72 are all LEDs. The flap position indicators are different, The quantity of emergency equipment are different. The most important of all, The both aircraft have the same identical engine. ATR 72 has long fuselage but in most of the countries, it is not flown with full capacity in mountainous territories as its engine power not suitable for high rate of climb with full capacity load so no use of large fuselage.