Strip gradient

[pudestcon]

I'm reading a book called "Flight At Lower Levels" by John Freeman.

 

I was particularly interested to read "If the gradient exceeds 2% (1:50) all takeoffs should be made down the gradient and all landings up the gradient."

 

Now I see a lot of strips that, in my estimation, exceed the 1 in 50 gradient John writes about; and I don't see this statement being observed.

 

What are your views on the statement in the book and do you follow this procedure?

 

Pud

 

 

[Guernsey]

Generally speaking Yes but it would also depend on the height of objects at the end of the take off runway. ( trees etc ). Alan.

 

 

[Student Pilot]

Any hill at all, always take off downhill no matter what the wind. John knew his stuff.

 

 

[Guest Crezzi]

Any hill at all, always take off downhill no matter what the wind. John knew his stuff.

Its a good book & I've no doubt John knows his stuff but it was written 15-20 years ago about the GA aircraft of that time. I don't think its quite so black & white as you suggest for those modern ultralights which don't need the curvature of the earth to get airborne.

 

Cheers

 

John

 

 

[frank marriott]

Short answer - Look at the "P" charts for the particular aircraft you are flying on the day.

 

As a discalmer I am a convert from GA so I am assuming the aircraft you are flying have detailed "P" charts if not ignor my comment.

 

Frank

 

 

[Guest davidh10]

Short answer - Look at the "P" charts for the particular aircraft you are flying on the day. As a discalmer I am a convert from GA so I am assuming the aircraft you are flying have detailed "P" charts if not ignor my comment.

 

Frank

The comment is still relevant without "P" Charts, as every pilot should understand the performance of their aircraft under different conditions, such as down-wind take-off and landing, which is particularly relevant to this thread.

 

The problem with rules of thumb as quoted from the book, is that it assumes a particular set of circumstances. Always understand the limitations of rules of thumb and where they may not be applicable or the best option. Even when a rule of thumb says regardless of anything else, it is still assuming a range of circumstances imaginable to the author at the time.

 

As an example of uncertain applicability, suppose you have a runway where the ends are lower than the middle. It is uphill or downhill? Could depend on the length of the runway and also whether you land short or long!

 

 

[Student Pilot]

As David said, first of all know your aircraft, if you don't know by expirence then use the aircraft manual and p charts.

 

Yes that Book of John's was written a while ago and aircraft have changed, law's of physics haven't.

 

If the tailwind is too bad you can't take off downhill and downwind, then stay on the ground. A wind coming over a hill will give you all sorts of grief both where you get airbourne and at the other end if you attempt to take off into wind and up hill. You won't believe how much difference up hill does make, if you get a chance try just going to the low end and accelerating up hill so you can throttle off before you get off the ground. Another trouble with taking off up hill mostly there is rising ground either after the end of the runway or a bit further on. A combination of false horizon effect and degraded performance from slow uphill takeoff can be a bad situation.

 

Taking into account all of the above, take of downhill every time.

 

 

[farri]

Where performance charts are not available, the decission should be made by considering all topographical features, the performance of the particular aircraft, the weather conditions prevailing at the time, and not least, the ability of the pilot.

 

Frank.

 

 

[Guest davidh10]

A couple of nice YouTube videos. Read the descriptions that tell the story.

 

• Just to complete the process, here's the landing, also uphill.
   
   
  

 

 

There's some other nice videos by the same author, including aeros in Australia.

 

 

[facthunter]

An uphill slope will certainly degrade the speed achievable, in a given distance but so does long grass or soft earth. Taking off downwind has it's own hazards. You need to achieve a higher groundspeed to lift off and you may encounter windshear as you attenpt to climb. This will affect your ability to stop the aircraft (as does a downhill slope), and clear obstacles on climb out' It's quite diffficult to estimate the amount of windshear, but there will always be SOME. The wind is always at a lower velocity at ground level than at height. Nev

 

 

[Guest Crezzi]

You won't believe how much difference up hill does make, if you get a chance try just going to the low end and accelerating up hill so you can throttle off before you get off the ground.

The last time I tried this was on a runway with a 12% gradient. I flew the length of the runway at 20' with less than max power and landed on the opposite end. This was intentional as it was the first brief flight after the plane had been reassembled (admittedly a very large mountain would have prevented me going much further in that direction - it really was a one way strip)

 

Cheers

 

John

 

 

[Yenn]

I don't know what the actual gradient at Rodds Bay is but I always take off uphill unless the tailwind is more than about 10kts. reason being that there is nowhere much to go with an engine failure at T/O going downhill.

 

 

[maddogmorgan]

Rules are for the adherence of fools and the guidance of wise men...or women

 

Always look at all the variables that may be involved.

 

 

[facthunter]

Don't fly by numbers.. be situationally aware. Nev

 

 

[Kyle Communications]

I am not sure what the gradient is on my strips but they are noticeably uphill. When the 4 aircraft came in to christen the strip they landed uphill and took off uphill. 2 of savs and 2 of 701...maybe its different for these "stol" aircraft. The attached link goes to the video and you will see none of them had any difficulty taking off uphill with a pretty severe crosswind. The wind was coming from about 70 degrees from the right off the nose at around 20 knots that day. it was the saturday of the Monto flyin so most will remember how bad the wind was that day if you went to the flyin. It was almost crosswind at my strips you can see by the dust trails..the strips had only been dozed about 3 weeks before so it was still mostly dirt.... but they are looking pretty good now :)

 

 

 

 

 

[rocket1172]

Hi guys. A whole lot of factors have to be considered on the day in question. but they have to be put into an order of priority. I did my Ag training with Col Pay in Scone, and he taught me land uphill and take off downhill regardless. Gravity is much harder to overcome than a tailwind. We used to take off with a tailwind regularly, but with enough airstrip to do so. 60 kts is always 60 kts, but you would normally take longer to get there, but by taking off downhill, gravity gives you a little extra boost to overcome the tailwind, so they kinda cancel each other out. Just be careful and think about the takeoff, even before you land there in the first place. Happy flying!

 

 

[poteroo]

1% downhill is worth probably better than 2 kts of headwind..... and, as everyone has noted previously, it's about what the terrain is like on the uphill side. Generally, strips are located on the lower slopes in the landscape - with the terrain rising more steeply above the top end. No chance of outclimbing that! As well, mountain winds can be very flukey. I'd always opt for good old gravity rather than any wind.The pic is Ompkali, EHD of PNG with around 14% uphill slope, and 800m length....if I remember rightly. Here, you added power on landing, even in a 500HP twin. On t/o, your distance to reject was about 100m.I think part of the risk in uphill takeoffs is that you will touch again if the wind drops slightly - and this reduces your acceleration lots more than you might think. The really problematical strips are those without any windsock = inaccurate wind estimations.

 

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