Almost all Whitehead biographers – both pro and contra – have confused his daughter's statement about a batch of fifty orders for motors. She's often misquoted as having said he'd received fifty orders on one day. What she actually said was, he'd "returned fifty orders on one day" (because he was too busy to complete them). 

"Whitehead's daughter, Rose, states that when she brought home the mail she had, more than once, so many letters with orders and advance payments on engines that she could scarcely hold them. In one of her 1930 interviews she reported that her father had returned fifty orders in one day."



The number of motors Whitehead built was not limited to

aeroplanes

(New York, Pittsburgh, No. 21, No. 22, Hargrave, Custead, Horsman, Arnot/Herring,  Dvorak, House, Hall, Beach, Lawrence, Shaffer, Wittmann, Miller, Wilson)  

Helicopters

(Burridge), and

dirigable balloons

(Baldwin, Meyer, Honeywell, Hamilton).

Aside from the irrigation pump motor he built for Buffalo Jones, Whitehead is known to have built many motors for boats:

"Junius Harworth said that Whitehead often constructed engines for local people to place in their boats. One engine was sold to an actor named Lawrence from New York for the sum of $1800. The father of Cecil A. Steeves had received one of these engines, his son reported." (Before the Wrights flew, S.Randolph, p. 128)



"Rose Whitehead Rennison, the eldest of the couple's three daughters, recalled that her father received so many orders and advance payments for engines that he simply returned them."

Orginally in "Aviation History Magazine, 1988" & later online here:

http://www.historynet.com/gustave-whitehead-and-the-first-flight-controversy.htm