Why is a Black Hawk helicopter circling Thetford?

The throbbing roar of a helicopter faded and returned repeatedly for close to an hour on April 10th over the Rices Mills, Tucker Hill Road, and Union Village areas of Thetford. And that was not the first time a helicopter has been observed flying around and around in an oval circuit above this part of town.

According to the website Flightradar24.com,  these were Blackhawk military helicopters out of Concord, New Hampshire. Of course, no-one knows their purpose. Perhaps it was to train a new pilot, but surely there are suitable training sites closer to Concord than Thetford. 

Or maybe these were nostalgic returns to Thetford after the Blackhawk training exercises by the army in 2023 at the Post Mills Airport.This included a daylight and a nighttime helicopter landing complete with weapon-touting soldiers. The public was assured that the weapons were not loaded.

According to the VT Daily Chronicle, Black Hawk helicopters are also being deployed in Vermont to patrol the northern US border 

Whatever the purpose, there must have been a good reason because that circling would have burned between 300 and 400 gallons of aviation fuel. Burning that fuel to just lighten the load doesn't make sense for a helicopter because, under normal circumstances, helicopters can land with a full fuel tank, unlike commercial jetliners. For a large commercial jet, the difference between their fully fueled takeoff weight and a desirable landing weight can be more than 200,000 lbs. If a large airplane is forced to land shortly after takeoff due to an emergency, it has to empty its fuel tanks somehow to get to proper landing weight. The pilot can fly round and round to burn off the fuel, which is time consuming. Or it may be more expedient to just dump the fuel, which can be ejected at the rate of several thousand pounds per minute. That said, it is possible for a large passenger jet to land with full fuel tanks, but it places enormous stress on the airplane's frame, and the whole aircraft must be thoroughly inspected afterwards.

Apart from Blackhawks, the most common helicopter in Thetford skles is the helicopter ambulance run by DHART (Dartmouth Hitchcock Advanced Response Team) and UVM Medical Center. Between them, they operate a fleet of four EC135 helicopters. Incidentally, the DHART helicopters have a distinct shape, with an oval body and a straight tail ending in a big tail fin, while the body of a Blackhawk tapers from cockpit to tail.

With around 5,000 airplanes in the sky at any given moment in the US, it's no surprise that there are more than helicopters overhead. 

A major flight approach to New York for international commercial jets runs roughly northeast to southwest across our region, with many appearing near or over Thetford. In under one hour, Flightradar reported jets from Madrid, Zurich, Naples, Brussels,  Amsterdam, and Stockholm, as well as two US Airforce jets, one a Boeing Stratotanker that is used by the military for mid-air refueling.

 Smaller airplanes criss cross this international flight path from many different places, including small airports like Lebanon and Whitefield, New Hampshire.

 But, no worries, the large passenger jets are cruising at an altitude between 30,000 and 42,000 feet where they take advantage of reduced atmospheric density for greater speed and fuel efficiency. They also fly above clouds and storm systems to minimize turbulence. Mid-size aircraft seem to keep to about 20,000 feet, and smaller airplanes to 5,000-7,000 feet. Little planes, like the Cessna Skyhawk, usually cruise between 3,000 and 15,000 feet, where they experience more weather changes, wind, and rain. Helicopters fly between 2,000 and 10,000 feet. At these altitudes the air density is sufficient for rotor lift and control. In fact, helicopters are designed for low-altitude flights that make them ideal for medical evacuation, search and rescue, and law enforcement. And, perhaps, for sightseeing over Thetford Center.