positive landing?
Join Date: Jul 2004
Location: UK
Posts: 849
Likes: 0
Received 0 Likes
on
0 Posts
It's an expression pilots use to explain away the unfortunate side-effects of gravity when they bury their kite into the tarmac, usually coupled with some sort of weather-related phenomenon only visible to the handling pilot. 
Join Date: Oct 2000
Location: slightly left of you
Age: 43
Posts: 362
Likes: 0
Received 0 Likes
on
0 Posts
I always do positive landings, but that's only because at the very last second i see a bump in the tarmac, and as a favour to all who follow me i try to flatten it. Otherwise all my landings would be smooth as silk
Torstennnn, no embarrassment when asking questions, (only when providing slick or irrelevant replies).
A positive landing in the sense of avoiding hydroplaning, is a landing where the aircraft vertical speed is sufficient for the tyres to ‘cut’ through a thin layer of water and make a good ground contact to achieve quick wheel spin up.
Numerically, depending on aircraft type and the ‘feel’ of the landing gear, normal landings are in the range 2-4 ft/sec, many much less (‘good’ ones); 6 ft/sec may be uncomfortable, and 10 ft/sec the approved maximum (but not necessary the limit).
Thus, when landing on a wet surface with puddles, or one which is prone to flooding (3mm depth), aim to achieve a vertical speed at touchdown towards the high end of normal. In particular avoid a smooth, low vertical speed contact or any opportunity to ‘skip’ (mild bounce where the landing gear extends but the wheels may not leave the runway).
There are of course many other variables and avoidance techniques for hydroplaning, but a positive landing helps to reducing one of the initiating conditions.
A positive landing in the sense of avoiding hydroplaning, is a landing where the aircraft vertical speed is sufficient for the tyres to ‘cut’ through a thin layer of water and make a good ground contact to achieve quick wheel spin up.
Numerically, depending on aircraft type and the ‘feel’ of the landing gear, normal landings are in the range 2-4 ft/sec, many much less (‘good’ ones); 6 ft/sec may be uncomfortable, and 10 ft/sec the approved maximum (but not necessary the limit).
Thus, when landing on a wet surface with puddles, or one which is prone to flooding (3mm depth), aim to achieve a vertical speed at touchdown towards the high end of normal. In particular avoid a smooth, low vertical speed contact or any opportunity to ‘skip’ (mild bounce where the landing gear extends but the wheels may not leave the runway).
There are of course many other variables and avoidance techniques for hydroplaning, but a positive landing helps to reducing one of the initiating conditions.
Warning Toxic!
Disgusted of Tunbridge
Disgusted of Tunbridge
Join Date: Jan 2005
Location: Hampshire, UK
Posts: 4,011
Likes: 0
Received 0 Likes
on
0 Posts
I believe that advice about positive landings to avoid aquaplaning in standing water conditions is now changing. I have seen it suggested that you should just go for a normal landing, and not have the cabin crew thinking you are a ham (which you are)!
Rainboe “…advice about positive landings to avoid aquaplaning in standing water conditions is now changing.”
Interesting, any link or source?
Would the change imply that the risk of hydroplaning has reduced, or if not, what alternative defences would be available?
Any such change appears to contradict other evidence, e.g. high pressure tyres and their particular type of manufacture (radial belt) may lower the hydroplaning speed.
Hydroplaning of modern aircraft tires – page 265, caution large file – 12mb.
An alternative would be improvements in runway surface and drainage, but there is little control over these aspects and operators can be caught out by changes in normal use, i.e. ‘slippery when wet’ categorization. See previous NASA research.
“ … thinking that your are a ham.”
Surely not, pilots require skill to achieve a positive landing. Like any change from normal operation, additional judgment and finesse may be required. A positive landing is not practiced routinely; pilots normally aim for a very smooth landing. The danger in the need for change is in misjudgment, a heavier than normal landing occurs where the crew might have to decide on an airframe check before the next flight; now that would be ham.
Interesting, any link or source?
Would the change imply that the risk of hydroplaning has reduced, or if not, what alternative defences would be available?
Any such change appears to contradict other evidence, e.g. high pressure tyres and their particular type of manufacture (radial belt) may lower the hydroplaning speed.
Hydroplaning of modern aircraft tires – page 265, caution large file – 12mb.
An alternative would be improvements in runway surface and drainage, but there is little control over these aspects and operators can be caught out by changes in normal use, i.e. ‘slippery when wet’ categorization. See previous NASA research.
“ … thinking that your are a ham.”
Surely not, pilots require skill to achieve a positive landing. Like any change from normal operation, additional judgment and finesse may be required. A positive landing is not practiced routinely; pilots normally aim for a very smooth landing. The danger in the need for change is in misjudgment, a heavier than normal landing occurs where the crew might have to decide on an airframe check before the next flight; now that would be ham.
Join Date: Jul 2004
Location: Sydney NSW
Posts: 513
Likes: 0
Received 0 Likes
on
0 Posts
safetypee?
Things are changing for future aircraft. Some months ago I felt I had to remove a post on brakes, landing gear, tyres because of the outcry and that I feared my then employer might put two and two together. The latest information you seek won't be linkable or be freeware yet. But the state-of-the-art at last farnborough is old hat now, we all of us have moved on but I don't know which of us is ahead in which areas. Doesn't help for present day ops but I assure you, what was published nine years ago at a symposium is valid only for the technology then, certified and fitted to an aircraft near you. Things really change but it takes time to bring it all certified on line. If you are at this farnborough look for a really fat australian and buy him a beer! As for rainboe, you been reading my book then? Oh gawd, you can't advertise here, the moderators kill you. So cancel my last. Have you been reading the best published work on brakes, landing gear and tyres then rainboe? Nice to see you back old son!
Best Rgds
The "E"
Best Rgds
The "E"
...advice about positive landings to avoid aquaplaning in standing water conditions is now changing...
The aquaplaning speed is determined by the tyre pressure alone. How you touched down previously is irrevelant.
Checkboard, Re; “it never existed.”
Where’s the evidence? Myths should be exposed if untrue, or is this one misunderstood?
Re your; “The aquaplaning speed is determined by the tyre pressure alone.”
According to many experts this is not entirely correct; the depth of tyre tread and runway surface texture are important parameters.
For a myth, then consider the ‘classic’ equation 9_/Tyre Pressure as the ‘aquaplaning speed’. An important aspect is the tyre spin up speed which has been shown to be much lower e.g. 7_/Tyre Pressure.
I would encourage you to read the links in #11.
Where’s the evidence? Myths should be exposed if untrue, or is this one misunderstood?
Re your; “The aquaplaning speed is determined by the tyre pressure alone.”
According to many experts this is not entirely correct; the depth of tyre tread and runway surface texture are important parameters.
For a myth, then consider the ‘classic’ equation 9_/Tyre Pressure as the ‘aquaplaning speed’. An important aspect is the tyre spin up speed which has been shown to be much lower e.g. 7_/Tyre Pressure.
I would encourage you to read the links in #11.
I wrote an article a while back about aquaplaning - and you are right about tread depth etc. The above wasn't supposed to be a rehash of the article, just pointing out that no study (that I have researched - and I have looked) has ever suggested that firm landings effect aquaplaning after the landing has occurred. Indeed your own post doesn't suggest that.
Beau_Peep
Join Date: Apr 2007
Location: India
Posts: 228
Likes: 0
Received 0 Likes
on
0 Posts
forget to derotate...
Positive (or in other words hard) landing occurs when you forget to derotate a bit while sinking and about to touchdown... I usually give a bit of forward push to the sidestick below 10ft.. that reduces the rate of descent of the main wheels and thats my saving grace.. 
cheers
cheers