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By Wilma
#1608313
Hi,

I recently visited Newquay and after studying the plate I noticed that one of the taxi ways (A) has a sloped section on it.

From its junction with Taxiway Charlie to 650 m short of holding point Alpha 3, Taxiway Alpha exceeds the required transverse and longitudinal slopes. Advisory warning signs are positioned at the beginning and end of the up and down slope. Pilots are to exercise caution in this area especially in conditions of surface contamination or when following other aircraft.


This made me wonder what is the maximum slope angle my aircraft is "certified" (?) for ?? PA34 Seneca V

I looked through the POH and couldn't see anything regarding this.

I have done various google searches and found the maximum taxiway slope angle EASA allow (3% for cat A & B) (CS ADR-DSN.D.265 Longitudinal slopes on taxiways) - but nothing that actually tells me what my aircraft is certified for.

I guess taildraggers manoeuvring down a downhill slope must also have a similar concern.

Does anyone know where you can find this information ?? (and does anyone know what the maximum longitudinal slope angle a Seneca V can negotiate (before it falls back onto it's tail) ??

I guess I can push weight as far back as allowed (in M&B) and jack up the front to see - but i thought I'd ask first.

Many thanks !
#1608463
Shirley, it's just simple geometry?....if you know where the rearmost loaded C/G lies, and where the MLG grounds, you can simply use a protractor on the centreline of the CG... If the projected vertical of the line CG- ground, falls within the wheelbase, the aircraft will be stable....though it will be less stable as the C/G to ground vertical reaches the edges of the ground within the wheelbase. sketch the planform on a piece of cardboard, make an accurate CG centreline....glue a cheap protractor, baseline going through the CG centreline, dangle a piece of weighted thread/ string from the CG point.

You can now tilt the silhouette to your heart's content and read the angle directly.

Really, all you need is the centreline and the wheelbase at the right distance from it....the silhouette is optional :wink:
The same system works equally well laterally.
Hey! I'm not even a pilot and I left school 56 years ago.....must have learned something!

Someone will put me back in my box if i'm wrong, you can bet! :D
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By Wilma
#1608547
Thanks for the response.

So my aft CoG limit is 94.6" and my rear undercarriage is 109.8" aft of the datum point (so is 15.2" further rearwards than my aft limit).

At 28 inches undercarriage height, I calculate that angle to be 28.5 degrees.

That would be quite a slope it is able to climb balance wise.

Edit: The front undercarriage is 10 inches higher and set 84.5 inches further forwards, so the aircraft already has a 6.75 degree slope which I would need to subtract from the figure given above.
Last edited by Wilma on Wed May 02, 2018 9:23 am, edited 1 time in total.
User avatar
By Sooty25
#1608784
I see nothing in your calculation @cockney steve, that allows for;

taxi speed,
bumps in the surface at slab joints,
wind speed,
wind direction
elevator position
maximum and minimum weights at aft CoG
(I'm sure I've missed a few)

I wouldn't suggest relying on your calculation with a couple of degrees knocked off for good measure!
By Wilma
#1608819
Where I was coming from was that Newquay warn pilots about the slope exceeding the maximum allowed slope angle for a taxi way - but then seems to place responsibility with the pilot.

My point was - I don't really know what my maximum slope angle is as it is not in the POH - so I was wondering if anyone knew where these were published - and if not - how I would determine what it is.

So far the theoretical calculation looks reasonable (assuming my calculation is correct) - and in my case provides for a considerable angle - probably much, much more than I am going to need - before taking into account observations like you have made above.
By TopCat
#1608824
I would have thought that power available to climb up it, and more importantly, braking available to not roll down it into the aircraft in front, will be more relevant than a tipping angle.

That's clearly what the advisory:

Pilots are to exercise caution in this area especially in conditions of surface contamination or when following other aircraft.


was about.
User avatar
By mikehallam
#1608825
Even of flat ground (grass,) injudicious power application can fairly easily make my tail wheel jump up, especially if the brake snatches or one wheel enters a small pothole. So any down slope will reduce one's margins in a tail wheeler.
As for nose wheel a/c I'd have thought they were better off in that respect ?
What wasn't specifically mentioned yet in this discussion was where (say) on strips taxiing can hairy on a sideways slope !

mike hallam.
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