737-100/200 VMO/MMO

[Johnny Tightlips]

Hi all

I recently bought a 1968 737 operations manual off ebay. I came across something interesting regarding VMO/MMO. In this manual it says that "VMO indicated ranges from 350 knots at sea level to 367 knots at 23,456 feet and then transitions to 0.84M". I always taught that it was just 350/.84 and nothing more. I'm just wondering if Boeing decided to make the VMO of 350 standard all the way to 0.84M or did the FAA's certification rules change at some stage.

I would also be intrested to know why the 300-900 is limited to 340/.82.

Thanks in advance.

[john_tullamarine]

The quoted characteristic is quite typical, Vmo being an EAS consideration which gives the IAS variation.

It is likely, I suggest, that your constant Vmo source was a simplified airline direction solely to make the exercise easier for crew memory.

However, one expects that the barber's pole reflected the variation. My memory of the instrument is getting a tad scratchy but, as I recall, that was the case for our birds.

The actual AFM variation which you see on the gauge will be an amalgam of the various things which go into the melting pot for determining Vmo during the certification process .. EAS to CAS to IAS conversions, gust loadings, bird strike, etc. Figuring the actual story by reverse engineering might be an interesting exercise but probably a tad frustrating at the end of the day ..