US Navy Accelerometer to Neg 12 G's?

2banaviator · **Posted:** Wed Aug 09, 2017 4:00 pm

I'm trying to determine what US Navy aircraft might have been equipped with an Accelerometer that measured from negative 12 to positive 12 G's.
I'm speculating that its from the late 1940-early 1950's due to the design of the indicator. It's the 3.25 inch diameter, not the 2 inch used in later aircraft. It has a USN anchor symbol stamped on its rear, hence the thought that it was a USN aircraft.

Most Accelerometers that I've seen from this era indicate a range from negative 4 to positive 12 G's. A lower range to negative 12 G's seems very unusual.

Any ideas?

Here's the indicator, below, and more photos are here: https://aeroantique.com/products/accelerometer-g-meter-1.

Fouga23 · **Posted:** Thu Aug 10, 2017 3:48 am

That is extreme :/

Dave Hadfield · **Joined:** Sun Sep 17, 2006 10:31 pm **Posts:** 1672

It's for when you're flying in Australia, and you're already upside-down.

That way the negative becomes positive, and so you're actually good for plus-12 both ways, on one gauge.

airnutz · **Posted:** Thu Aug 10, 2017 10:23 am

Mebbee used in test programs or regular operational conditions where you want to track extremes encountered? D-558 program, helicopters or aircraft landing on a pitching deck, landing traps in carrier ops? The Navy operates in some pretty demanding environs.

2banaviator · **Posted:** Thu Aug 10, 2017 10:37 am

A little bit of WIXer humor is always welcome, thanks!

This indicator is particularly interesting in that it suggests that the aircraft that had it installed might occasionally (intentionally or unintentionally?) maneuver such that the pilot would experience up to negative 12 G's. So what might that maneuver be? And for what practical purpose would that serve (e.g., toss-bombing)? Or if experiencing neg 12 G's as a result of error, what is the error and why was it expected to occur at such frequency that the aircraft had to have an indicator for those instances?

Perhaps this is an example of my pondering the imponderable... but some aeronautical engineer identified the necessity to have this in an aircraft of the US Navy and I can't help but ask Why?

K5DH · **Posted:** Thu Aug 10, 2017 12:13 pm

Maybe it's out of some kind of test apparatus, rather than an aircraft?

Pogmusic · **Posted:** Thu Aug 10, 2017 3:26 pm

Centrifuge?

Fouga23 · **Posted:** Thu Aug 10, 2017 3:36 pm

Those values would be deadly if real.

CoastieJohn · **Joined:** Fri Feb 11, 2011 5:37 pm **Posts:** 1380

K5DH wrote:

Maybe it's out of some kind of test apparatus, rather than an aircraft?

I was thinking along those lines also. I did see one that was -5 to +12 that was stated to be from certain models of B-17's and B-25's. The other wag would be some kind of early test aircraft.

2banaviator · **Posted:** Thu Aug 10, 2017 4:22 pm

CoastieJohn wrote:

K5DH wrote:

Maybe it's out of some kind of test apparatus, rather than an aircraft?

I was thinking along those lines also. I did see one that was -5 to +12 that was stated to be from certain models of B-17's and B-25's. The other wag would be some kind of early test aircraft.

Thanks CoastieJohn. The accelerometer that you're recalling is likely the AN-5745 (Type B-3), used in some models of B-17 and B-25 during post WWII, but also in other aircraft post WWII (e.g. F9F). It was also made by Kollsman, but also by Bendix (Pioneer) and Jaeger.

Unlike the AN-5745, which had 3 pointers, one for actual (real time) Gs, and one each for max and min Gs experienced in flight (as a record) until reset, this example only has one pointer to indicate Gs in real time without any max/min indication. So the (presumed) pilot viewing the reading is apparently responding to it (e.g. thinking 'holy sh-t') in real time.

CoastieJohn · **Joined:** Fri Feb 11, 2011 5:37 pm **Posts:** 1380

2banaviator wrote:

CoastieJohn wrote:

K5DH wrote:

Maybe it's out of some kind of test apparatus, rather than an aircraft?

I was thinking along those lines also. I did see one that was -5 to +12 that was stated to be from certain models of B-17's and B-25's. The other wag would be some kind of early test aircraft.

Thanks CoastieJohn. The accelerometer that you're recalling is likely the AN-5745 (Type B-3), used in some models of B-17 and B-25 during post WWII, but also in other aircraft post WWII (e.g. F9F). It was also made by Kollsman, but also by Bendix (Pioneer) and Jaeger.

Unlike the AN-5745, which had 3 pointers, one for actual (real time) Gs, and one each for max and min Gs experienced in flight (as a record) until reset, this example only has one pointer to indicate Gs in real time without any max/min indication. So the (presumed) pilot viewing the reading is apparently responding to it (e.g. thinking 'holy sh-t') in real time.

There is a pic out there of the AN-5745 for sale. That is where I got the application info. The pic of the one you posted is for sale on several sites....unfortunately there is no amplifying info as to the application.

Cutlass · **Posted:** Fri Aug 11, 2017 11:15 am

The F7U-3 could demonstrate 16 positive G's as well as 9 negative G's without structural harm. However, it uses the smaller accelerometer.

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US Navy Accelerometer to Neg 12 G's?

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