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General Information

Starting a Staggerwing engine is not an easy task. For instance the Pratt & Whitney is not a simple task of pressing a starter and sitting back. The pilot must coax and cajole the engine into life. Get it right and the engine will never fail and gleefully splutter into life (listen to the example below), get it wrong and it will simply laugh at the pilot and refuse to start.

A pilot ideally needs three hands during the start up sequence. One to is used to raise the fuel pressure using the wobble pump, it's handle is usually mounted on the right side of the forward cabin. The other two hands must dart all over the panel setting fuel taps, master switches, magnetos, mixture, throttle, primer. All the time he needs to keep the fuel pressure up using the wobble pump and then finally hit the starter and hold your breath. 

Get it right and the engine will wheeze, cough, splutter and come to life, smothering the propeller, engine cowl and lower wing in a cloud of thick oily smoke. The odor of oil and aviation fuel lingers in the cabin for a few minutes, before quickly clearing. Once opened up for take off the powerful engine will lift the Staggerwing into the air in a trice. I recently flew in one with no headwind assistance and four adults on board. Within just a few aircraft lengths we left the ground. Once in the air a Staggerwing will easily climb at 1500ft per minute a go on to 5 miles high and cruise at over 200mph.

Pratt & Whitney R-985 "Wasp Junior"

The Pratt & Whitney R-985 "Wasp Junior" Engine is probably the most common engine to be found in Staggerwings today. Mainly because most Staggerwings flying today are of the model D-17S which had this engine fitted from new. The R-985 air-cooled engine was first used by the Air Corps in 1932. At that time, it was rated at 300hp and over a two year period it rose to 400hp. During World War II the engine was improved and became a 450hp engine and at this point found its way into the Staggerwing. The R-985-AN is now a 9-cylinder, air-cooled, supercharged radial engine with a displacement of 985 cubic inches. With a maximum RPM of 2,300 it can produce 450 hp and lift a Staggerwing with four passengers into the air very short distance and easily cruise at speeds around 200mph.

Throughout it's life this engine has been favoured by military aircraft and installed in thousands of different makes and models. It has also been used to power numerous civilian aircraft.

On a careful run the "Wasp Junior" can deliver fuel consumption in the region of 15gph (gallons per hour). If flown hard on full throttle this can easily rise to around 20gph.

During the preflight checks it is imperative to turn the engine manually by turning the propeller by hand through 360 degrees several times. This process checks that there are no hydraulic locks. Hydraulic lock are created by oil draining into the piston chamber. This non compressible fluid will cause severe engine damage should the engine be started with such a lock.

Jacobs "Shaky Jake"

This engine was favoured by Walter for some of his earlier Staggerwing models and also later more economical models.

The Jacobs Radial Engine, nicknamed "Shaky Jake", began it's life in 1930 as a 3-cylinder engine producing 55hp and 7-cylinder producing 150hp. The 3-cylinder was soon made redundant with the 7-cylinder becoming the engine that would be developed over the years.

In 1934 the L-4 was produced and it is this model which Walter chose to use for his Staggerwings. The L-4 used fore-and-aft rocker arms of classic design. The L-4 developed 225hp from 757 cubic inches. The 831 cubic inch, 285hp L-5 was produced from 1936 and was the largest American seven until the post war Cyclone Seven was built.

The "Shaky Jake" used coil ignition instead of the normal magneto and the distributor caps were prone to cracking. This lead to the spark being delivered to the wrong cylinder and resulting in a rough running engine. The cure was to put the cap through a bakeout in a vacuum oven and then impregnate the crack with insulating varnish. Following this process the cap would normally run a normal life without giving further trouble. That would normally be fine, except it was an illegal process and the US government requested that it was replaced by a new cap that was not prone to this cracking.

The "Shaky Jake's" fuel consumption was in the region of 15gph. 

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Pratt & Whitney