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Member postings for David Mellor

Here is a list of all the postings David Mellor has made in our forums. Click on a thread name to jump to the thread.

Thread: What Happens Next
13/02/2018 12:57:49

@The Wright Stuff....

You might be taking the comment somewhat out of context.

The actual context was, in essence, fell walking which is what I do solo when I go slope soaring. As none of my slopers have propellers there is no prospect of losing any fingers. Also, mobile phone signal varies between none at all and patchy at best.

The reason I mention it is not to be pernickety, but to emphasise that the balance of risks that each of us accepts varies according to actual circumstance. I don't think there is any chance that anyone could lose all 4 fingers of one hand, though.......?

13/02/2018 09:24:09

Well said.

Thread: Proposed new drone legislation/registration
11/02/2018 13:51:55

Well done BEB, and thank you for your efforts.

11/02/2018 12:09:27


Quote: "That's not strictly true. I fly with telemetry and set warnings - and I've experimented with automatic throttle cuts - for the current 400 foot ceiling that we have at our site for 7kg models. While not everyone has this luxury, many radios are now capable and in a club environment, it shouldn't be too hard to find someone to demonstrate the appearance of some different sized models at 120m."


Martin....what is your altitude telemetry actually measuring? I would think it may be measuring barometric pressure and subsequently calculating an equivalent height above datum. That method works reasonably well over flat ground. But doesn't work well over very steep ground.


So whilst you will get a meaningful read-out of altitude flying over a flat field site, the read-out of altitude whilst slope soaring over very steep ground will be largely meaningless. Real-time estimates of altitude based on GPS signal will also be largely meaningless over very steep ground.


To be blunt about it, there isn't a practical way to measure the vertical distance between a model plane and very steep ground in real time. Therefore legislation which proscribes a vertical distance greater than 120meters between an aircraft and the ground would be technically impossible to comply with for slope soaring (at least on big slopes).


Fortunately I think the answer is simple. The "drone law" isn't actually concerned with this (slope-soaring AGL-altitude) issue at all. So slope-soarers need not worry about it.






Edited By David Mellor on 11/02/2018 12:11:51

11/02/2018 11:10:57

I've had a (very) quick trawl through the documents in the list you kindly provided.

There is no recognition (that I could find) that steep terrain and AGL-altitude-ceilings are logically incompatible, even though they plainly are in the case of slope soaring.

So all is well and we needn't be concerned.

If the forthcoming legislation makes no mention of it then it simply isn't a problem for slope soaring. The authorities clearly have much bigger fish to fry.

11/02/2018 10:31:28

Thanks Steve, I'll trawl through them.

I'm not opposed in principle to the legislation.

As a retired scientist it rather suddenly (and belatedly) dawned on me that there is a logical error in using an AGL-ceiling over steep ground if the locus of the measurement moves with the aircraft. It isn't rocket science, but it is definitely wrong and irrational if they proceed on that basis. Fortunately it would also be unenforceable too.


11/02/2018 10:03:58

Steve, well I'm glad someone has commented on the AGL/slope problem. It sounds like you are on the case - well done.

I'm a bit shocked to learn that this process has taken 3 years with no response to comments.


11/02/2018 10:00:25

cymaz - sheer guess and hope for the best is exactly what I do too. So do we all. I think thats the point.

11/02/2018 09:58:34

Dave, the idea of rounding an estimate to the nearest 100 feet makes perfect common sense. Moreover, it is what you would expect from an experienced, competent pilot. And it is what we have been doing for years.

And for slope-soaring no-one has previously been asked to consider the distance between the aircraft and the ground vertically below the aircraft.

But now the situation may be changing. If a ceiling based on AGL altitude is adopted, then you would need to be able to estimate how much the distance between your plane and the ground below it is when that ground is falling (sloping) away from you. Thats what an AGL altitude is.

The practical solution is to allow the slope soaring pilot to keep the aircraft AGL value relative to the fixed launch point rather than the steeply dipping ground below the actual moving aircraft. But thats not what the draft rules appear to say because (it seems) no one has thought very hard about slope soaring in relation to AGL ceilings.

11/02/2018 09:45:24

Steve, what I've done about it is raise it here for discussion. BEB tells us that it would seem no-one has considered this before.

Why haven't I commented on the EASA prototype or NPA or respond to DfT consultation or written to my MP?

Well, that is 4 questions. But the answer is the same in each case. I first realised that there was problem yesterday afternoon. So I have had less than 24 hours to do anything other than raise it here for discussion.


Edited By David Mellor on 11/02/2018 09:48:11

11/02/2018 09:41:16

Dave - a limit of 50 feet altitude above a hill top simply isn't a problem.

What we are talking about is the opposite situation in which you mustn't let the ground fall more than 120 metres below your aircraft!

11/02/2018 09:39:18

Cymaz - even if you could determine AGL from the plane (you can't) you would still have the problem that the real altitude AGL increases rapidly in level flight if you fly over steep ground.

For a slope soarer this is a ridiculous situation because he has to fly out into wind over ground that is rapidly falling in elevation (thats what a slope is). Therefore even in level flight the slope soarer will very quickly exceed 120m AGL. But given that the flight-objective from launching down-dip into wind is to gain altitude in the first place, it is essentially impossible for any slope soarer to comply with a 120m AGL limit.

The problem isn't to do with slope soaring itself. The problem is to do with an arbitrary definition (of 120m AGL ceiling) that hasn't been thought through for anything other than flat terrain.

11/02/2018 09:30:41

Dave .... I think you are right.

How then have we landed ourselves in a position where it seems we may be required to control slope aircraft to meaningless criteria? And.... what is the BMFA doing about it?

11/02/2018 09:21:30




Having thought about "the slope soaring problem" a bit more, it seems to me it has two aspects:-


1. The term "Ground Level" (or GL) is an oxymoron when applied to steep terrain.


2. It is impossible for any pilot to determine altitude-AGL in real time


It follows then, that if the concept of a ceiling of, say, 120m AGL is somehow enshrined in rules that there is no prospect of slope soaring being able to comply. Even flat-field flyers have to make some approximations since they can only determine an AGL altitude barometrically.


What makes all this seem irrational to me is that the possible ceiling figure (120m AGL) is so precise (to the nearest ten metres). That is because it is an approximate conversion from a rough number (400 feet) in one unit to different unit (stated to the nearest 100 feet). The difference in implied precision between the two is 10 meters (about 33 feet) compared to 100 feet of the original wet-finger-in-the-air guess of a 400 feet ceiling.


I know some folk will say I'm being pernickety in raising this. But that isn't true. If your definition (AGL in this case) doesn't meaningfully apply to some circumstances that you need to account for and if your measurement system (altitude AGL over slopes) is impossible to determine and if you are unwittingly tightening the implied precision required to control to...........why then, you have a problem.


Note for BEB - I'm not aiming these comments at anyone in particular, and certainly not at the messenger!.




Edited By David Mellor on 11/02/2018 09:27:15

10/02/2018 22:57:35

An interesting area for future discussion then.

Regarding your point about clubs, BEB, I don't know how other slopers operate. I am a member of an Soaring Association, but as the name suggests it is simply a loose affiliation of people - it isn't a formal organisation and it has no rules nor does it have a structure of officers. But it has been around for donkey's years and has a good record.

Well, time will tell I guess, but if there is any opportunity to raise the specifics of sloping then I feel that someone ought to..........

10/02/2018 13:08:33

I have a question about the meaning of 120m AGL in practical, real-world terms.

I slope soar from the side (not the peak) of a steep fell in the Lakes. I soar out towards a road which is two to three hundred meters down-dip but around 100 metres lower than launch GL.

In level flight (down-dip direction) the glider will be gaining AGL altitude at a rate as high as 1 metre per second.

But down-dip soaring (into wind in other words) from a slope is the standard method to gain altitude. So if I gain an absolute altitude from launch of, say 100 metres, the glider could easily be 200 m AGL or more over the road.

So the question is this:-

What is the lateral range (or scope if you prefer) of an altitude limit of 120 m AGL with respect to terrain gradients and line-of-site control distances for model aircraft (slope soaring) control?

Supplementary: clearly the concept of an AGL limit isn't an issue on flat-field sites. Slope soaring (the clue is in the name) sites are not flat.

Thread: What Happens Next
10/02/2018 09:47:36

I fly alone in the lake district where I live. I slope soar on fells miles from the nearest village. If anything untoward happened to me then a "situation" might soon develop.

I have had offshore-survival and first aid training, though that was decades ago. It does install a lot of common sense, however, and a sense of the importance of self-reliance. Taking some very basic survival gear is important - including a good knife to cut up clothing to stuff into and/or tie off wounds. Mobile signals are patchy.

The biggest risks that I think I face are incapacitation (from heart attack or fall-injury) and subsequent hypothermia. The solution, as ever when outdoors, is to leave information with a dependable person as to location and return times and take basic kit with you.

My other interests before becoming a bit decrepit have included rock climbing, skiing, scuba diving, caving and sailing. In all these activities there has to be an acceptance of, and coming to terms with, the risks associated. Annually, all of these activities see some undesirable level of death and serious injury.

To the best of my knowledge (happy to be corrected) the annual rates of death and serious injury (limb loss, sight loss etc) in flying model airplanes is zero to BMFA members.

Life is short - enjoy what you do while you can. There is an old adage that may help: "if you think you can do it, you are right, if you think you can't do it you are right". What do you think?

09/02/2018 19:39:44


09/02/2018 19:15:56

If one has a sense of grandeur then it is as well to have company during one's final moments in order to record one's last words.

Perhaps the most fitting to this thread might be those of Denis Diderot - French philosopher who expired July 1784.

He said (in French, naturellement) "But how the devil do you think this could harm me?"

09/02/2018 18:36:03


A sense of proportion helps, allied to a bit of common sense.


Perhaps we should start another alarmist thread on the hazards of coconuts. Or beds. Or the weather.


Approximately 150 deaths annually are caused worldwide by falling coconuts, along with hundred of injuries.


Nearer to home, in a typical year in the UK 5 people will die from lightning strikes and around 20 from simply falling out of bed in the morning.


A male, over-60 years of age BMFA member's risk of death or serious injury is dominated by a very long list of factors wholly unrelated to propellers. In the UK in a typical year some ten thousand people are injured from pulling on their socks (assuming the grim reaper didn't pick them off when they tumbled out of bed in the first place).


Get a life. And enjoy it while it lasts.......

Edited By David Mellor on 09/02/2018 18:38:17

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