In terms of seat recline, what is the conversion from inches to degrees?

8 replies

074061

Cathay Pacific - Asia Miles

Member since 25 Apr 2013

Total posts 262

In terms of seat recline, what is the conversion from inches to degrees?

charlieg

QantasFF Platinum

Member since 16 Feb 2012

Total posts 133

because of the varying height of seats, there is no correlation between reclining angle and reclining inches

074061

Cathay Pacific - Asia Miles

Member since 25 Apr 2013

Total posts 262

I see

11sjw

Member since 11 Mar 2012

Total posts 159

I believe the "inches" measurement measures how far a point on the headrest / top of seat moves.  The only "conversion" would be as a function of seat height and basic geometry.  

Phil Young

Qantas

Member since 22 Oct 2012

Total posts 193

The issues of seat pitch (separatioin between seats) in inches, and the angle of recline (in degrees) are completely seperate issues.  On one hand they are unrelated, though of course are both critical to passenger enjoyment.

watson374

Qantas - Qantas Frequent Flyer

Member since 17 Aug 2012

Total posts 1,285

This involves some trigonometry, so I've drawn a diagram for the lols.

It's not true that they are unrelated - they are, they're both measurements of recline - but I don't think anyone in this thread has actually thought through how to convert these. My formula is based on finding the length of a chord (the recline in inches) using the radius (the height of the seatback) and the angle subtended at the centre of the chord (the difference between the maximum and minimum angles of recline in degrees). Note that if you're using the formula to convert recline from inches to degrees, you'll only be able to find out the recline in degrees from the 'upright' position.

074061

Cathay Pacific - Asia Miles

Member since 25 Apr 2013

Total posts 262

Thanks. It'll take me a few minutes to calculate that, but thanks. The sin rule right?

watson374

Qantas - Qantas Frequent Flyer

Member since 17 Aug 2012

Total posts 1,285

If you're only using the isosceles triangle formed by the two extreme seatback positions recline in inches, you could use the cos rule to calculate the recline from the upright position. This involves square numbers, though, but is also a perfectly valid method.

In this case, the formula would be:

where all symbols carry the same meaning as in my first formula.

Thanks for bringing up the sin rule and letting me derive another formula. I have tested both formulae and they both work - both return an identical result and both match my scale drawing.

I hope this proves useful, at the very least as something to do on a regional LCC flight with no IFE!

TheRealBabushka

Member since 21 Apr 2012

Total posts 2,059

Hey Watson,

This post is fantastic and relates to the query I raised today.

Assuming the height of the seat back is constant, a greater distance of recline = a larger degree of recline?

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