Shoreham R31 in a 152
Let's see:
Take-off
Runway 31, length 425m + 190m starter extension = 615.
Cessna 152, standard take-off distance 410m. x 1.1 grass factor x 1.33 safety factor = 600m.
600m <625m.
Slightly marginal, but okay so long as you use all of the runway starter extension.
Landing
Runway 31, length 425m, but no landing extension.
Cessna 152, standard landing distance 366m x 1.1 grass factor x 1.43 safety factor = 575m.
425m<<575m !!
If flying out to land somewhere else, yes. If planning a routine landing onto 31 at Shoreham - NO.
Yes, of-course, an experienced pilot who knows their aeroplane should be fine, but anything goes wrong and the insurance company, (other) aircraft owners and AAIB will be less than polite about it - so why do you need to?
G
Take-off
Runway 31, length 425m + 190m starter extension = 615.
Cessna 152, standard take-off distance 410m. x 1.1 grass factor x 1.33 safety factor = 600m.
600m <625m.
Slightly marginal, but okay so long as you use all of the runway starter extension.
Landing
Runway 31, length 425m, but no landing extension.
Cessna 152, standard landing distance 366m x 1.1 grass factor x 1.43 safety factor = 575m.
425m<<575m !!
If flying out to land somewhere else, yes. If planning a routine landing onto 31 at Shoreham - NO.
Yes, of-course, an experienced pilot who knows their aeroplane should be fine, but anything goes wrong and the insurance company, (other) aircraft owners and AAIB will be less than polite about it - so why do you need to?
G
Join Date: Jan 2003
Location: The Heart
Posts: 811
Likes: 0
Received 0 Likes
on
0 Posts
IO540,
A wind gradient, you mean, being a change in the speed and/or direction due to friction with the surface.
Wind shear being a sudden change in wind speed and/or velocity.
A wind gradient, you mean, being a change in the speed and/or direction due to friction with the surface.
Wind shear being a sudden change in wind speed and/or velocity.
Join Date: Jun 2003
Location: EuroGA.org
Posts: 13,787
Likes: 0
Received 0 Likes
on
0 Posts
It's only a question of degree.
In the world of gas flow, there is no such thing as "sudden".
The reason wind shear can cause crashes is because some planes (notably jets) are unable to increase their airspeed fast enough to overcome the loss of airspeed due to the headwind reducing on final approach.
Pistons are usually more able to cope with wind shear, though I know of a TB20 owner who was trying to land with a surface wind of about 55kt (straight down the runway) and busted the nosegear (and the prop, etc). With a 55kt reported surface wind you can expect a big loss of airspeed - even between the top of the pole where it is measured and the surface.
In the world of gas flow, there is no such thing as "sudden".
The reason wind shear can cause crashes is because some planes (notably jets) are unable to increase their airspeed fast enough to overcome the loss of airspeed due to the headwind reducing on final approach.
Pistons are usually more able to cope with wind shear, though I know of a TB20 owner who was trying to land with a surface wind of about 55kt (straight down the runway) and busted the nosegear (and the prop, etc). With a 55kt reported surface wind you can expect a big loss of airspeed - even between the top of the pole where it is measured and the surface.
Join Date: Jul 2000
Location: My views - Not my employer!
Posts: 1,032
Likes: 0
Received 0 Likes
on
0 Posts
Gengis,
Nice answer, may I expand for a laugh?
To make the landing public transport legal you would have to reduce the landing distance by 23%. According to the 152 POH that I saw, I remember a 10% reduction in landing distance per 9kt HWC. I asume that this is the reason for Oka asking about R31 in the first place. So to get that reduction in landing distance, lets factor in enough headwind to get the 23% reduction:
so 2.3*9 = 21kt.
Now the CAA safety sense leaflet says that you may only use a half of the headwind component for landing distance performance corrections. So we must factor the minimum HWC:
21 * 2 = 42kt HWC.
For a POH approach speed of 54kt, that gives a ground speed of 12kt. I wager the ground roll in these circumstances may be around 20m? (or 4% of the LDA)
Love numbers!
ps. If anyone out there approaches an airfield with a 42 kt HWC at 54Kt indicated, could you contact me first so I can:
1. Get the AAIB on site to record the crash
2. Call the fire service for you...
3. Clear the undershoot so no innocent parties are hurt!
Be safe! Never do anything in this game you couldn't explain to your mum, and then a judge.
Nice answer, may I expand for a laugh?
To make the landing public transport legal you would have to reduce the landing distance by 23%. According to the 152 POH that I saw, I remember a 10% reduction in landing distance per 9kt HWC. I asume that this is the reason for Oka asking about R31 in the first place. So to get that reduction in landing distance, lets factor in enough headwind to get the 23% reduction:
so 2.3*9 = 21kt.
Now the CAA safety sense leaflet says that you may only use a half of the headwind component for landing distance performance corrections. So we must factor the minimum HWC:
21 * 2 = 42kt HWC.
For a POH approach speed of 54kt, that gives a ground speed of 12kt. I wager the ground roll in these circumstances may be around 20m? (or 4% of the LDA)
Love numbers!
ps. If anyone out there approaches an airfield with a 42 kt HWC at 54Kt indicated, could you contact me first so I can:
1. Get the AAIB on site to record the crash
2. Call the fire service for you...
3. Clear the undershoot so no innocent parties are hurt!
Be safe! Never do anything in this game you couldn't explain to your mum, and then a judge.
Very good Cough.
Aged about 25 (which sadly was a long time ago) I was in the scarily responsible position of managing a number of training and fast jet aeroplane performance and handling trials (occasionally from the back seat). Fortunately I had a very experienced boss who was very ready with helpful advice, and was working with some very very high ability pilots, who were more than happy to point out bluntly if I was about to screw up (or just had done!)
One bit of advice from my boss that I've repeated often in my mind was: "Before making any decision, always run through your mind the phrase 'at the subsequent board of enquiry'".
I've been lucky not to make too many aviation cock-ups since, but the biggest was certainly one where I'd failed to heed that excellent bit of advice, and I try hard never to forget it again. It was, incidentally, also related to landing performance calculations.
G
N.B. I don't have a C152 POH to hand, but don't recall it actually allowing for proverse factors, only adverse ones. Can anybody confirm or deny?
Aged about 25 (which sadly was a long time ago) I was in the scarily responsible position of managing a number of training and fast jet aeroplane performance and handling trials (occasionally from the back seat). Fortunately I had a very experienced boss who was very ready with helpful advice, and was working with some very very high ability pilots, who were more than happy to point out bluntly if I was about to screw up (or just had done!)
One bit of advice from my boss that I've repeated often in my mind was: "Before making any decision, always run through your mind the phrase 'at the subsequent board of enquiry'".
I've been lucky not to make too many aviation cock-ups since, but the biggest was certainly one where I'd failed to heed that excellent bit of advice, and I try hard never to forget it again. It was, incidentally, also related to landing performance calculations.
G
N.B. I don't have a C152 POH to hand, but don't recall it actually allowing for proverse factors, only adverse ones. Can anybody confirm or deny?
Thread Starter
Join Date: May 2008
Location: UK
Posts: 525
Likes: 0
Received 0 Likes
on
0 Posts
This flight actually went well and i'd guess I used about 1/3-1/2 of R31 including ground roll. Regarding Ghengis' figures:
Landing
Runway 31, length 425m, but no landing extension.
Cessna 152, standard landing distance 366m x 1.1 grass factor x 1.43 safety factor = 575m.
Is the safety factor not just for public transport ops? I don't recall that in the PPL and it would preclude going to a lot of smaller airfields.
Landing
Runway 31, length 425m, but no landing extension.
Cessna 152, standard landing distance 366m x 1.1 grass factor x 1.43 safety factor = 575m.
Is the safety factor not just for public transport ops? I don't recall that in the PPL and it would preclude going to a lot of smaller airfields.
Join Date: May 2006
Location: Londonish
Posts: 779
Likes: 0
Received 0 Likes
on
0 Posts
Maybe you do things differently round here, but I'd rather expect to find takeoff weight, density altitude, and headwind component present in both the takeoff and landing calcs? They tend to have a rather marked effect on the distance used!
Join Date: Nov 2000
Location: Cambridge, England, EU
Posts: 3,443
Likes: 0
Received 1 Like
on
1 Post
Maybe you do things differently round here, but I'd rather expect to find takeoff weight ... present in both the takeoff and landing calcs?
At what size aircraft does the actual weight start to get used (routinely, not just by people who are trying to shave a couple of metres off their requirement)?
Join Date: May 2006
Location: Londonish
Posts: 779
Likes: 0
Received 0 Likes
on
0 Posts
Interesting (by the way, that wasn't supposed to be a flippant or sarcastic post, though in retrospect it probably read that way).
I got my PPL under a different regime (australia); I've always used everything on every takeoff calculation - headwind, tailwind, surface (short grass hard base / long grass, soft base). As standard a certain amount of margin is mandated to be built into the POH, which I wouldn't touch - POH figures all the way.
Then having arrived at a final number, my personal practice was/is to make a judgement call on how close to that number I'm willing to go, based on a whole bunch of factors: currency and familiarity, confidence in the numbers, stability of any headwind, predictability of the surface (grass in particular being a very variable animal - encompassing anything from almost as good as concrete to absolute treacle - how a single grass factor can be published I don't know!)
I'm no sky god, but personally I'd rather know what the theory says, then fudge some safety onto that, than use a very conservative estimation tool that gives a factored number - and make a go-no-go on that number; My thinking is that at least I have a feel and awareness for how hard I might be pushing it vs the other system where I'm not making the call. Of course, if you get down to making decisions based on single digits it's probably time to take a long hard look!
I got my PPL under a different regime (australia); I've always used everything on every takeoff calculation - headwind, tailwind, surface (short grass hard base / long grass, soft base). As standard a certain amount of margin is mandated to be built into the POH, which I wouldn't touch - POH figures all the way.
Then having arrived at a final number, my personal practice was/is to make a judgement call on how close to that number I'm willing to go, based on a whole bunch of factors: currency and familiarity, confidence in the numbers, stability of any headwind, predictability of the surface (grass in particular being a very variable animal - encompassing anything from almost as good as concrete to absolute treacle - how a single grass factor can be published I don't know!)
I'm no sky god, but personally I'd rather know what the theory says, then fudge some safety onto that, than use a very conservative estimation tool that gives a factored number - and make a go-no-go on that number; My thinking is that at least I have a feel and awareness for how hard I might be pushing it vs the other system where I'm not making the call. Of course, if you get down to making decisions based on single digits it's probably time to take a long hard look!
Guest
Posts: n/a
I wonder where the Cessnas I used to fly got their performance from? I don't recognise any of the figures as 'real'
Solo with 2 hrs fuel, 150s and EVEN 152s are quite agile.
Load any a/c to mauw and start factoring and you can find excuses not to operate all of them.
Don't get drawn in by declared distances on grass aerodromes. In golfing terms the playable often extends beyond the limits imposed from the Belgrano.
Have a look at Derby
Be safe, but be real - and have fun.
SGC
Solo with 2 hrs fuel, 150s and EVEN 152s are quite agile.
Load any a/c to mauw and start factoring and you can find excuses not to operate all of them.
Don't get drawn in by declared distances on grass aerodromes. In golfing terms the playable often extends beyond the limits imposed from the Belgrano.
Have a look at Derby
Be safe, but be real - and have fun.
SGC
Join Date: Dec 2005
Location: Here and there. Here at the moment but soon I'll be there.
Posts: 758
Likes: 0
Received 0 Likes
on
0 Posts
It's only a question of degree.
In the world of gas flow, there is no such thing as "sudden".
The reason wind shear can cause crashes is because some planes (notably jets) are unable to increase their airspeed fast enough to overcome the loss of airspeed due to the headwind reducing on final approach.
Pistons are usually more able to cope with wind shear, though I know of a TB20 owner who was trying to land with a surface wind of about 55kt (straight down the runway) and busted the nosegear (and the prop, etc). With a 55kt reported surface wind you can expect a big loss of airspeed - even between the top of the pole where it is measured and the surface.
In the world of gas flow, there is no such thing as "sudden".
The reason wind shear can cause crashes is because some planes (notably jets) are unable to increase their airspeed fast enough to overcome the loss of airspeed due to the headwind reducing on final approach.
Pistons are usually more able to cope with wind shear, though I know of a TB20 owner who was trying to land with a surface wind of about 55kt (straight down the runway) and busted the nosegear (and the prop, etc). With a 55kt reported surface wind you can expect a big loss of airspeed - even between the top of the pole where it is measured and the surface.
If you have experienced it you would know that there is much more to it than what you alude to in your response above. All aircraft types can be severely affected by it, and at anytime, not just when landing.
