When you think of the words “workhorse” and “helicopter”, the CH-47 Chinook is more than likely one of a number of aircraft that immediately jump to mind. The Boeing-Vertol team that developed the Chinook from the Model 107 (which also spawned the CH-46 Sea Knight) struck gold, developing the concept into one of the most recognizable heavy lift helicopters in existence today. Able to successfully fly a variety of different missions, and with a tolerable price tag attached (especially given the capabilities the Chinook could provide battlefield commanders in terms of troop transport, logistics and supply), the CH-47 was pretty much the badass do-everything helo the US Army needed during the Vietnam War and beyond. Among the various features built into Chinook to increase its survivability, durability and versatility in combat zones was one more suited towards use in special operations warfare- it could land on water for short periods of time.
The Vertol Model 107 was itself designed with a water-landing capability, manifested in the CH-47, which was significantly larger and more elongated than the 107. To provide a degree of buoyancy, the Chinook’s designers added sealed-off compartments within the sponsons that exist on both sides of the aircraft’s fuselage. The hull itself was made watertight, with critical components carefully sealed off to prevent water damage. Though pilots understandably were extremely reluctant to test out the aircraft’s durability ratings, including while on water, the Chinook gave them a comfortable safety margin- it could withstand conditions up to Sea State 3 (waves at a maximum height of 1.6 to 4.1 feet). While the Chinook couldn’t really remain afloat for lengthy, sustained periods of time, it was still more than enough for special operations purposes. The US Army did wind up making use of the Chinook’s amphibious capabilities, first in Vietnam, with the covert deployment and recovery of Special Forces (SF) and members of the legendary Military Assistance Command-Vietnam’s Studies and Observations Group. The primary factor that limited the frequency of such missions was the corrosive nature of seawater. Engines and exposed machinery would have to be meticulously cleaned and serviced upon the aircraft’s return to base, sidelining the helo and making it unavailable to fly more missions until it was cleaned up fully and returned to duty.
Years later, the CH-47 still is a big part of spec ops aviation, especially with the famed 160th Special Operations Aviation Regiment, which uses MH-47D/Es to move US Army Rangers, Green Berets, Navy SEALs, Delta Force operators and the like, around in combat zones. But the Night Stalkers of the 160th aren’t the only ones who utilize the Chinook in such a way. Take the Royal Air Force’s No. 7 Squadron, based out of RAF Odiham. No. 7 traces its roots back to the First World War, but adopted the special operations role only [somewhat] recently in 1982 after a seven-year inactivation. Stood up to provide a transport support service to the Special Air Service and Special Boat Service after the Falklands War, when British military commanders realized the value of possessing a dedicated unit of the sort. Among the many crazy things both No. 7 pilots and Night Stalkers are trained to do is the Delta Queen extraction, which exploits the Chinook’s water-landing capabilities.
The Delta Queen maneuver tends to occur at the recovery stages of spec ops missions which involve extracting a team (and their watercraft) from rivers, seas, etc. in a quick and timely manner, allowing for a quick egression from the area of operations. If the mission calls for a water-based extraction (i.e. the Delta Queen), the spec ops warfighters will typically coordinate their removal while en route to a pre-designated pickup point in a Zodiac watercraft. The pilot of the Chinook slated to grab the incoming troops brings his aircraft to a hover above the surface of the water, while gradually lowering the altitude of the helo until it comes to a slight float on the water. Aircrew in the rear of the helo have, meanwhile, lowered the main ramp fully, ready for the inbound Zodiac. Since the Chinook is now resting on the water’s surface, though maintaining a bit of vertical lift, the cargo hold fills up with water. As the Zodiac approaches, crew stay close to the walls of the hold or move to the rear, while one crewmember uses a red light to wave the spec ops team in. The operator of the Zodiac’s outboard motor now has to race the engine, while keeping his craft perfectly in line with the hold. One misstep could potentially spell out disaster for both the team and the Chinook and its aircrew. As soon as the boat whips into the hold, the ramp is raised slightly while the pilot lifts the aircraft from the water. As the hold empties of its liquid contents, the Chinook banks away and the Delta Queen exfiltration is complete.
Pretty cool, don’t you think?