#ch-46

Helicopters that have two main rotors mounted fore and aft, instead of a traditional tail rotor are known as tandems. They've been around as long as conventional helicopters but are not as widespread.

From bottom up: HUP Retreiver, CH-21 Shawnee, CH-46 Sea Knight, CH-47 Chinook

Despite there being several notable tandem rotor helicopters only one seems to stand out to the greater public and has its name known - the Chinook. Which is why every tandem now gets called as such, especially the CH-46 Sea Knight.

The CH-46 came first and was designed and built by Vertol (later by Boeing) for the US Navy and Marine Corps. The Army wanted something bigger and more beefy than what the CH-46 offered so Vertol started with a redesign that eventually became the CH-47. The two went on to operate beside each other during the Vietnam War and for a few decades after. The CH-46 was finally retired in 2015 but the CH-47 is still in service with the Army and in several other countries.

What do they have in common? They're both large, twin engine, tandem rotor helicopters with three blades each, and they served as heavy lift transport and utility helicopters for the US military. What differences do they have? Quite a few but this will focus on the main external features to tell them apart at a glance.

Side by side the differences between them become more apparent.

This a CH-46 Sea Knight.

And a CH-47 Chinook.

Beginning with the nose, a Chinook's protrudes while the Sea Knight is more sloped along with the windscreen.

Next, the Chinook has a four place landing gear with two wheels on the front gear while the Sea Knight has tricycle type with two wheels on every gear. The main landing gear is attached to sponsons in both aircraft but the shape of the sponsons is different.

In the Chinook they run mostly the length of the fuselage. In the Sea knight they are much smaller and streamlined at an upward angle of incidence.

The last most notable difference to tell them apart at a glance are the engines. The CH-46 Sea Knight uses two, more narrow turboshaft engines that are embedded at the base of the aft mast. The intakes are facing forward and the exhausts point 90° out to either side.

The CH-47 uses larger and more powerful turboshaft engines that are mounted on the rear fuselage in pylons on either side of the aft mast. The engines usually have a filter screen at the forward facing intake and the exhaust points straight back.

So in summary to tell apart the CH-46 from the CH-47: sloped nose vs pointed nose, four point landing gear vs tricycle landing gear, small sponsons vs large sponsons, and small embedded engines vs large external engines. If you can identify one or more of those things then you can accurately tell a Sea Knight from a Chinook.

Try it out now in fact. Here are a BV-107 and BV-234, the civilian versions of the CH-46 Sea Knight and CH-47 Chinook. They are operated by Columbia helicopters and painted in the same livery. Can you tell which is which?

CH-46 from HMM-265 trailing smoke and flame after being hit by PAVN anti-aircraft artillery. The helicopter crashed and exploded upon impact, killing 13 marines

A Boeing Vertol CH-46D Sea Knight prepares to land on the helicopter pad of USS New Jersey (BB-62), on February 1, 1985.

Photographed by Walter M. Urban Jr.

“Marine of the 1st Battalion, 3rd Marines, leaves CH-46 Helicopter during Operation Thor-PhaseII just south of DMZ.” 7/6/1968

McCullough, photographer. File Unit: Divider/Subject - 218 - Helicopters CH-46, 1962 - 1975. Series: Black and White Photographs of Marine Corps Activities in Vietnam, 1962 - 1975. Record Group 127: Records of the U.S. Marine Corps, 1775 - .

Now at the National Archives Museum:

Remembering Vietnam: Twelve Critical Episodes in the Vietnam War  Learn about the origins, controversies, and legacy of the Vietnam War through twelve critical episodes.

A perfect perch....

A United States Marine observes his mother ship, United States Navy  amphibious assault ship USS Bonhomme Richard (LHD 6), recede in the distance....from his perfect perch aboard a departing CH-46A helicopter....on a magnificent day in the Coral Sea near Australia.

Sure would be the thrill of a lifetime to occupy that same choice spot aboard the CH-46!

                              Marines board a CH-46A helicopter.

                                      ______________________

>>CLICK the top photo....and take a virtual seat....