Think I learnt about flying today...

[goatwhacker]

I had one of those "I learnt about flying from that" experiences this morning... Please note this is posted as a confession as honest as I can make it, with the intention of hopefully helping other pilots with my level of (in)experience avoid finding themselves in a similar position! I accept full responsibility for what happened... Background: I'm a 100hr PPL, just starting to feel 'comfortable' with the whole flying thing. This is, of course, dangerous...
Awoke to find a gorgeous CAVOK day, no wind at ground level. The aim was to go looking for a prominent landmark in the mountains about 20 minutes flying time from where I'm based. Appearances can be deceptive however. The area forecast said the wind at 2000' was a 20kt westerly. At 5000' it was 30kt. Alarm bells should have been ringing by now but no, I told myself it wouldn't be too bad. I think I saw the 'CAVOK' bit on the forecast, rejoiced and didn't look at much more in any detail. So I also missed the whopping great SIGMET for severe turbulence, didn't I!!!
We went flying. It went fine until we got to the foot of the mountains and a few bumps appeared. "She'll be right", I thought, and pressed on. :eek:
We got very very close to the goal when I made my only good decision on this flight - this was not becoming fun; time to get out of there. This was sadly followed by one of my poorer decisions: Rather than turning right and staying over relatively high ground, thus avoiding much of the weird stuff you get from wind near cliffs, I went LEFT. Which put me over a valley. And needing to pass over a ridge to get home. A few seconds later we copped a significant DROP and, as my pax were crawling down from the ceiling, I decided to climb as much as I could to get out of there. Full power, hold best rate of climb airspeed and look in horror at the VSI reading more than 1000fpm DOWN. OK, now I was getting very very worried, and that ridge was looking awfully close (we were well clear but it appeared closer than it was). Finally got the aircraft up to a relatively safe level, still a little bumpy until we cleared the ranges completely. Got back to the airfield and at least landed nicely, so got some brownie points back from the pax for that.
Not one of my better efforts all round. A few glaring errors:
1) Read the forecast PROPERLY!!! Wind can do funny things to aeroplanes.... wind over hills is NOT good! SIGMETs are there for a reason and I'm still at a loss to describe how I managed to miss something so vital (and obvious!).
2) Continuing on. Perhaps the biggest one, the 'press-on-itis' thing. I should have turned around well before I did. Even better, canned it on the basis of the forecast!
3) Turning out over the valley. Why I did that I'm also not sure.
4) Going in so close to terrain on a day with strong winds predicted. Of course it's going to be bumpy; I KNEW that. But went and did it anyway. I was at least 1000' clear of it at all times but it didn't feel like it sometimes!

And finally, bad mistake to take people who have not flown in a lightie into this sort of environment. I'm dirty at myself for that - especially given the people I had on board who are somewhat special to me.

I got away with it this time. The bag of luck is a little less full. I will learn from this one!!
Any comments welcome... what else vital did I miss??? :ugh:

GW

[MyData]

omigod

Full power, hold best rate of climb airspeed and look in horror at the VSI reading more than 1000fpm DOWN

Just reading that brought a knot to my stomach.

I try and learn at least something from every flight. I guess every now and then we learn a great deal from a flight.

[IO540]

What "mountains" were these? There are no mountains in the UK.

Nobody reads sigmets or airmets anyway so nothing unusual there.

But if wind flows over terrain then yes it can get bumpy. This is a good flyer on the subject:

http://www.caa.govt.nz/fulltext/Safety_booklets/Mountain%20Flying.pdf

There isn't too much of a problem with -1000fpm VS because the air isn't going to flow into the ground, so when you have descended to a few hundred feet, the downdraught should stop.

[goatwhacker]

...that would be because I'm not in the UK... ;)
The aircraft was within W+B limitations, the engine was developing full power and I'm buggered if I knew what to do after that!! apart from coax it back up.
when you have descended to a few hundred feet, the downdraught should stop.
Yeah it's just the 'descended to a few hundred feet' thing that worried me!! I was over a valley facing (if I went any lower) a pretty sheer cliff. OK maybe it's my inexperience talking here but it scared the bejeebus out of me.
But that's a great pamphlet, thanks mate. I'm now much much more aware of this sort of thing!!

[coodem]

I'll admit I did the same sort of thing the other day. Had to take my partner to the station around the corner from my local flying club @ 05:30, weather looked good, wind a little high, but at least no cross wind factor.

Did a pre flight, took off by the time I was at 500 feet I saw all the clouds nearing in, next minute I was in the middle of the whole lot. It was as if someone put the duvet over the aircraft. Could not even see the prop in front of me, I was around 1000ft AGL, Now I started to panic, never been in this situation, not even with an instructor.

Well it took me a few seconds to take control of the situation (felt like hours) Maintain safe altitude, keep the wings level and maintain airspeed.

I reached for the GPS in the rear, turned it on, as I was going to use any help I could get. Finally I got site of ground again, had the runway in site. I was so relieved. landed, got out, looked up at the sky and it was clear, just my luck. Thought about going up again, but thought I had enough "excitement for the day

Just to make it clear my only intentions for the flight were to do a few circuits, a few touch and goes, or there was no way I would have gone up. (My airfield does not do conventional circuits, due to noise abaitments)

I now know I need to get a minimum of an IMC, just to deal with these brief, but yet so long moments

[IO540]

I really really do not wish to make the sort of smartar*e comments which are so common on certain other pilot forums, but

Did a pre flight, took off by the time I was at 500 feet I saw all the clouds nearing in, next minute I was in the middle of the whole lot. It was as if someone put the duvet over the aircraft.

suggests that a big improvement in preflight (weather) planning is called for.

I reached for the GPS in the rear, turned it on

It should have been ON the whole time, checked for satellite reception before starting the taxi. Do you push start your car, and use the starter motor only when too tired or when parked uphill?

[coodem]

Do admit I only did a quick TAF, as no METAR available, closest was 20 mile away. Returned CAVOK and VIS 9999.

This was the case, apart from that unlucky cloud that seemed to follow me for what seemed ages. Probably making it sounds worse than it really was, but it certainly was one of my worst nightmares

I agree, GPS should have been turned on. It follows me everywhere, but as I was only planning to stay in the "circuit" I saw no point at the time.
BUT have since realised I was very wrong, Plan the unexpected, You never know next time I might have to divert for one reason or another.

[MyData]

IO540

There isn't too much of a problem with -1000fpm VS because the air isn't going to flow into the ground, so when you have descended to a few hundred feet, the downdraught should stop.

That stands to reason, and hopefully one day I won't have to remember this thread. But if you are in the scenario as posted I guess faith in where the airflow goes won't give you a great sense of satisfaction.

[Wycombe]

From your profile and your description of the circuits, I could take a wild guess at your base airfield :ok:

If you are where I think you are, the local weather (esp. cloud) may often be very different to that at a big airport generating TAF's just down the road.

....but I guess you know that now :)

[Vortigon]

What "mountains" were these? There are no mountains in the UK. Actually there are over 100 mountains in the UK I take it you were joking about this :) To the original poster I would advise perhaps a review of your met thoery on terrain/wind effects always helps to keep your theory fresh in mind with a deeper understanding of the wind changes/time of day effects etc even if you had missed the full weather broadcast you'd of been able to have a good idea of what to expect from observing the time of day/terrain type/cloud coverage etc As a learning experience its one you would be far better learning from condition observation and theory rather that your experience but at least it has maybe gave you a wake up call to review your flight routine planning and preparation.

[IanSeager]

There isn't too much of a problem with -1000fpm VS because the air isn't going to flow into the ground, so when you have descended to a few hundred feet, the downdraught should stop.
Quite a few aircraft have crashed in the mountains because of severe downdraughts. One in Switzerland a week or so ago.
http://is.blick.ch/img/gen/T/4/HBT4wDJP_Pxgen_r_304xA.jpg
Ian

[Confabulous]

Have to agree with Ian and others here, there's plenty of evidence to suggest that a downdraught can force you into the ground. A few airliner accidents too, which is the reason why windshear alerters were invented.

Besides, what if a microburst occurs near a mountain and you happen to fly over it? The burst won't stop, it'll just drive you into the mountain.

[tangovictor]

I thank " goatwhacker" & " coodem " for there honesty, if it wasn't for hearing of others " mistakes " learning could be, very costly indeed !

[gcolyer]

IO540

Why should his GPS have been switched on? It is not a pre-req to VFR or IFR flight, although i must admit it is nice to have.

[dublinpilot]

I think IO540's point is not that everyone must carry a gps and have it turned on.

It's more that if you carry a gps as an emergency aid, but wait until you are in an emergency to turn it on, it may already be too late.

A non IFR pilot who has inadvertently entered IMC doesn't need the distraction of having to reach into the back of the aircraft, search through their flight bag to find the gps, secure it to the dash, turn it and and program it with a flight plan. Way too much distraction.

Along with this is the fact that it will take a little time for it to acquire a fix, even longer because of the speed of the movement. Longer still if it hasn't been used for awhile. In the mean time the VFR pilot is likely to focus on the GPS trying to see if it has got a fix yet.

Much better to have it turned on, programed, and left aside if you don't what to use it. At least it's all ready to go if the emergency situation occurs.

There was a report some months ago of someone on the other place, failing to find their destination, and in failing light. They decided at that point to pull out their gps which they had made sure had fresh batteries. However it had been some months since they had last let the gps acquire a fix. This combined with the speed of movement of the a/c and possibly a poor view of the sky, meant that 20 minutes later the gps hadn't acquired a signal.

GPS are fantastic safety aids. But if you carry one for use in an emergency, it's far better to have it prepared before the emergency, rather than need to set it up when it happens.

dp

[IO540]

I don't see how a downdraught can force a plane into the ground.

In the cases referred to, I would bet that there were other factors. For example, somebody flying in a canyon which was too narrow to turn around in and/or had "bits" sticking out of the bottom, and then being forced down is going to put you in a situation which you cannot get out of (insufficient climb rate and/or insufficiently tight turn radius). From what I have read about deep canyon flying (called "mountain flying" by those that do it; to me, mountain flying means flying at least 2000ft above the peaks :) ), this sort of thing happens regularly, wind or no wind.

This topic cannot be adequately disposed of with one-line replies.

But a plain downdraught caused by air flowing down a mountain, with the plane flying over flat ground at the bottom of it, should not be able to force the plane into the ground. If it can, please explain the physics involved.

[tangovictor]

I think the original poster had answered this ! he had intended to fly circuits, surely no one would need gps to carry this out ?????

[Mercenary Pilot]

Large-Scale Vertical Waves (Mountain Waves)

Mountain waves occur on the lee side of topographical barriers and occur when the wind-flow is strong, 25 knots or more, and the flow is roughly perpendicular to the mountain range.The structure of the barrier and the strength of the wind determines the amplitude and the type of the wave. The characteristics of a typical moun-tainwave are shown in figure 3-3-9.


Figure 3-3-9 shows the cloud formations normally found with wave development and illustrates schematically the airflow in a similar situation. The illustration shows that the air flows fairly smoothly with a lifting component as it moves along the windward side of the mountain.The wind speed gradually increases, reaching a maximum near the summit. On passing the crest,the flow breaks down into a much more complicated pattern with downdrafts predominating. An indication of the possible intensities can begained from verified records of sustained downdrafts (and also updrafts) of at least 5,000 feet per minute with other reports showing drafts well in excess of this figure. Turbulence in varying degrees can be expected and is particularly severe in the lower levels; however, it can extend to the tropopause to a lesser degree. Proceeding downwind, some 5 to 10 miles from the summit,the airflow begins to ascend in a definite wave pat-tern.Additional waves, generally less intense thanthe primary wave, may form downwind (in some cases six or more have been reported). These are similar to the series of ripples that form downstream from a submerged rock in a swiftly flowing river. The distance between successive waves usually ranges from 2 to 10 miles, depending largely on the existing wind speed and the atmospheric stability. However, wave lengths up to 20 miles have been reported.It is important to know how to identify awave situation.


http://www.tpub.com/weather2/3.htm35.gif
Figure 3-3-9.—Schematic diagram showing airflow and clouds in a mountain wave.

Pilots must be briefed on this condition so they can avoid the wave hazards.Characteristic cloud forms peculiar to wave action provide the best means of visual identification.The lenticular (lens shaped) clouds in the upper right of figure 3-3-9 are smooth in contour. These clouds may occur singly or in layers atheights usually above 20,000 feet, and may be quite ragged when the airflow at that level is turbulent. The roll cloud (also called rotor cloud) forms at a lower level, generally near the height of the mountain ridge, and can be seen extending across the center of the figure. The cap cloud,shown partially covering the mountain slope, must always be avoided in flight because of turbulence,concealed mountain peaks, and strong downdrafts on the lee side. The lenticulars, like the roll cloudsand cap clouds, are stationary, constantly forming on the windward side and dissipating on the lee side of the wave. The actual cloud forms can be a guide to the degree of turbulence. Smooth clouds generally show smoother airflow in or nearthem with light turbulence. Clouds appearing ragged or irregular indicate more turbulence.While clouds are generally present to forewarn the presence of wave activity, it is possible for wave action to take place when the air is too dry to form clouds. This makes the problem of identifying and forecasting more difficult.

[Chilli Monster]

Did a pre flight, took off by the time I was at 500 feet I saw all the clouds nearing in, next minute I was in the middle of the whole lot. It was as if someone put the duvet over the aircraft.
suggests that a big improvement in preflight (weather) planning is called for.
Actually it doesn't. It means that, just occasionally (and it has happened to me) weather forecasters get it wrong.

I reached for the GPS in the rear, turned it on
It should have been ON the whole time, checked for satellite reception before starting the taxi. Do you push start your car, and use the starter motor only when too tired or when parked uphill?

Oh for F*CKS sake! :ugh:

Some people like to fly without GPS, some people like to look out the window, some people like to use a map occasionally. Flying isn't JUST about switching on all the gadgets and following the lines. Sometimes it's just nice to get out there and play, getting away for the world about you and doing things which others would give their eye teeth for. Sometimes it's just about tipping your wing into a cloud, flying some simple aero's, imagining you're something, somebody or somewhere else.

There are times when the GPS comments get really tiresome Peter - give it a break PLEASE!

(And can I also suggest a gliding course where Mountain Wave activity is coupled with hills and mountains - you'll garner a whole new respect for flying in such areas close to the surface).

[Confabulous]

There are times when the GPS comments get really tiresome... give it a break PLEASE!

I've just realised Chilli is absolutely right. In a way it's ridiculous to set yourself up like an airliner - we're mostly PPLs for god's sake, let's have a bit of fun. You can read all the accident reports, articles and opinions you want, but our flying is supposed to be fun, in a challenging way. I can't see the day we'll have a computer showing you which way to roll in aerobatics, how much G to pull, how close you are to stall alpha etc... it's getting damned ridiculous. Most PPLs are VFR only. Map reading is a good skill to have. So is weather reading.

Ernest K Gann said 'Rule books are paper - they will not cushion a sudden meeting of stone and metal.' Neither will your portable GPS if you fly into cloud with no IMCR or IR. Neither will the METARs and TAFs - they get it wrong too. There's been plenty of case of electrical failure leading to death, simply because they relied too much on the gadgets.

GPS is great - but it takes a lot of skill out of flying, sometimes when it's needed most.

[MayorQuimby]

I don't see how a downdraught can force a plane into the ground.

I guess as soon as you're flying upwind it can. I can see what you're saying as long as you're flying downwind, although that probably assumes nice non-turbulent flow.

I imagine too that people have been caught out by believing they could go over a ridge in a windward direction because they were above the ridge to start with. In this situation they may not have had the climb rate to maintain their altitude as they approached the peak, cutting through the descending airflow.

MQ.

[dublinpilot]

Some people like to fly without GPS, some people like to look out the window, some people like to use a map occasionally.

There are times when the GPS comments get really tiresome Peter - give it a break PLEASE!


I've just realised Chilli is absolutely right. In a way it's ridiculous to set yourself up like an airliner - we're mostly PPLs for god's sake, let's have a bit of fun.

Oh come on guys. IO540 never said that coodem (or anyone else) should always fly with a gps. He simply, and correctly pointed out, that turning it on after an inadvertant entry into IMC at low level was far far too late.

Does any seriously think that a VFR only pilot (and I'm assuming coodem is from his post) who has entered cloud at low level should be turning around looking for his gps on the back seat, then trying to fiddle around with it?

If he had it with him and turned on before the flight then it could be a big safety aid in the situation described.

If you carry a gps for the purpose of helping you out in an emergency aid then have it set up so that it can aid you if that emergency comes along. We all make sure that we wear our life jackets, and have the life raft close to hand when flying single engine cross water don't we? It's ready to go if needed.

If you enter cloud low level, VFR only, and the gps is in your flight bag, then I think you've already missed the boat as far as GPS goes. Forget about it, fly the airplane and use whatever you have to hand. That maybe a predetermined safety altitude, and tuned in vor, or simply the radio to call a radar unit for help. Trying to find and turn on a gps at this point is only going to disorient you.

If you carry equipment for an emergency then have it set up. If you don't, then don't distract yourself with it in the emergency.

dp

[englishal]

The thing is....if you have the forsight to carry a GPS, then why not have it switched on. Fine if you want to dead reackon your way around the land (or as Enerst K Gann said after using radio navigation: "we had to revert back to this old outdated dead reckoning" and this was possibly in the 40's ;) )....If you don't want to use it then either turn it away from you, don't look at it or leave it at home.........

A spare battery is no good for your torch if it is in you bag in the boot, or as I found out, there is no point leaving your approach plates in the bag in the luggage compartment just because the weather is *forecast* to be VFR....:O

[IO540]

I guess as soon as you're flying upwind it can. I can see what you're saying as long as you're flying downwind, although that probably assumes nice non-turbulent flow.

However, in the "flying next to a mountain" scenario you won't be flying upwind or downwind. You will be flying across the airflow (i.e. parallel to the mountain face). The wind is coming down the mountain, so if you did fly upwind you would fly into the rising ground (not good).

I imagine too that people have been caught out by believing they could go over a ridge in a windward direction because they were above the ridge to start with. In this situation they may not have had the climb rate to maintain their altitude as they approached the peak, cutting through the descending airflow

Absolutely agree. I just couldn't see how descending airflow could force a plane all the way into the ground - unless there are other factors.

As to those having a go at me over suggesting that a GPS should be switched on if it is being carried at all, I am suprised as some who did should definitely know better. A GPS in the bag, not switched on, is about as much use as a chocolate teapot.

I am trying to write stuff that expands knowledge on a subject. If everybody did the same it would be helpful all around. If somebody disagrees, it's better to post a good reasoned argument which I can learn something from, not Oh for F*CKS sake!

[Piltdown Man]

I believe Mercenary Pilot is right, it was mountain wave which was to blame for your predicament, or in your case, the rotor which is an associated phenomenon. And these things go down to the ground! In a glider, you often end up putting on as much speed as you can and fly into or directly down wind. In a powered aircraft I'd do the same (and I have done so!), but with full power!

What you missed was "wind and mountains" however cities lots of large buildings do very similar things. I bet you won't miss these two again.

PM

[SAR Bloke]

A downdraught can easily throw you into the ground. It is true that one of the escape methods for downdraughting is to head to lower, flatter, ground as the air will usually (but not always) become more laminar and may enable you to climb out of trouble. Turbulent air can do funny things and you can never rely on it.

Flying next to a mountain you can easily be into wind or downwind. Katabatic and anabatic winds flow up and down the mountain and, if the pressure gradient wind is perpendicular to the mountain you would be in either updraughting or downdraughting air depending on whether you are on the windward or lee side of the mountain. You can be into wind or downwind in updraughting or downdraughting air and vice versa. If the pressure gradient wind is parallel to the mountain then you would be predominately into wind or downwind.

As to having no mountains in the UK, I can guarantee that they are big enough and dangerous enough to catch out even the best pilots.

Mountain flying (including mountain weather and mountain winds) is a very complex and demanding subject. I would advise anyone contemplating it to read up on the subject first. If going mountain flying in winds greater than about 10-15kts then you may want to think about getting some advanced instruction in mountain techniques.

Goatwacker: Kudos to you for sharing your experience and glad to hear all ended well.

[Tuned In]

Does IO540 have some sort of obsession with GPS? My comment would have been exactly the opposite - I think he reached for GPS too early, unless he was just turning it on ready to use if the situation was not quickly resolved. It is very easy for someone to get focussed on something with a moving map at the expense of the flight instruments. There are other things that take priority, and other ways of resolving the problem that should be tried before reaching for the GPS to navigate. By the time they have been run through the GPS will have its first fix.

I think I'd quite like to fly with Chilli though.

[Fuji Abound]

I recall a similiar experience a few years back.

Overcast at around 5,000 feet, otherwise clear air, no local thunder storm activity, but maybe a cell around thirty miles to the south.

Level, low ground with a small ridge to the north up to 500 feet. Light wind.

At 4,500 feet I got caught in presumably a micro burst. With the engine at full chat I was getting a 1,000 fpm descent in totally smooth air. Fortunately there was a grass strip I know over my left shoulder, but at 500 feet and still descending, enountered light to moderate turbulence and air rising as quickly.

Never quite understood the events of that day or the circumstances that caused the micro burst. I always wondered at what height the descent would have stopped if I had not passed into the rising air.

I will also remember I thought for some while the problem was with the engine and couldnt understand why in spite of everything appearing normal I was descending at an alarming rate. Of course everything was normal! (at least so far as the engine was concerned).

[bookworm]

I think I saw the 'CAVOK' bit on the forecast, rejoiced and didn't look at much more in any detail. So I also missed the whopping great SIGMET for severe turbulence, didn't I!!!

CAVOK is good at lulling into a false sense of security. I made a flight a few weeks ago where everywhere was reporting CAVOK. When I arrived at my destination, it was still CAVOK. It was also 18 gusting 25 across a runway half as long and half as wide as I was used to, with a cliff at the end for good measure. The approach was ... interesting. ;)

[IO540]

Does IO540 have some sort of obsession with GPS?

Oh for F*CKS sake!
Some people like to fly without GPS, some people like to look out the window, some people like to use a map occasionally. Flying isn't JUST about switching on all the gadgets and following the lines. .

Let's examine the supporting evidence for the above statements, based on what I actually said in this thread...

It should have been ON the whole time, checked for satellite reception before starting the taxi. Do you push start your car, and use the starter motor only when too tired or when parked uphill?

As to those having a go at me over suggesting that a GPS should be switched on if it is being carried at all, I am suprised as some who did should definitely know better. A GPS in the bag, not switched on, is about as much use as a chocolate teapot.

So, I think some people are getting a bit over-excited. Must be the summer weather :O

[Chilli Monster]

It should have been ON the whole time, checked for satellite reception before starting the taxi. Do you push start your car, and use the starter motor only when too tired or when parked uphill?

This was what I was having a go at - why SHOULD it have been switched on. Why can't it be switched off. So the guy felt the need for it later. Fine - though I think getting the aircraft stable and in a situation where you won't impact cumulo granitus first would have been a better idea. You don't have the right to tell them what they should or shouldn't be doing - that's their decision.

You've banged the GPS drum enough - like I said before, give it a break - even the supporters get pi**ed off after a while. :rolleyes:

[Saab Dastard]

goatwhacker - great post, thanks for sharing your learning experience! You have definitely emptied your bag of luck a bit, but you have also filled up your bag of experience! :ok:

I don't see how a downdraught can force a plane into the ground.

IO, the thing is that descending air can and does descend all the way to the ground. When it hits the ground it "bounces" and spreads outwards. Unfortunately aircraft don't bounce so well!

This can be seen in "pure" vertical downdrafts - microbursts - which have been the cause of several large passenger jets hitting the ground on final approach. So severe is the problem in some states in the US that they have installed systems to warn ATC and aircraft of such microburst activity close to airports. Microbursts are usually associated with storm-cell activity.

Very similar effects can be experienced in the turbulent air on the lee-side of mountains and hills, particularly in the rotor area. You will find that there is frequently - not always - a component of the rotor that actually strikes the ground. A light aircraft caught in such a situation is unlikely to have sufficient power to overcome the downdraft.

Even in situations where the rotor or turbulent air does NOT actually strike the ground, an aircraft may STILL hit the ground due to its inertia - it takes a signifcant time to convert a high rate of descent into a climb, even if the air itself is not descending.

It is exactly the same as if you had dived towards the ground and pulled out too late. BANG!! :ouch:

I have a background in civil engineering (fluid mechanics) and I also have some experience of flying gliders in ridge-soaring and wave conditions - bottom line is that it really, really is possible to have an aircraft slammed into the ground by downdrafts in mountains.

SD

[QDMQDMQDM]

This accident report shows what happens when you end up in downdraughts on a lee ridge:

http://www.bfu.admin.ch/common/pdf/1730

Even if you don't read German, scroll down to the pictures, which tell the story.

[IO540]

You don't have the right to tell them what they should or shouldn't be doing - that's their decision.

Why post a story (of a near accident) in a public forum if not expecting suggestions?

[jetflite]

Thus leading to why Pilots of aircraft/helicopters approaching mountains from the lee side shall do so at 45degree angle, allowing sufficient time that if a sever down draft is incountered the aircraft can make a turning decent/climb away from the MOUNTAINS, ALWAYS have an escape route.

Originally Posted by IO540
I don't see how a downdraught can force a plane into the ground.

One of the most common forms of accidents are CFIT(controlled flight into terrain) including down drafts and microburst/clear airpockets,
all these play a dangerous part in aviation and are often over looked until you are unfortunate enough to encounter it and if survived it to always be aware of them. I my self experienced a Drop of 1500ft in a twin-engine aircraft to find my self 500ft above terrain and my No.2 engine to surging due to the negative G and engine feeding/fueling issues, Since then i can assure you that you constantly fly with an escape route over mountains! :ok:

[goatwhacker]

I will also remember I thought for some while the problem was with the engine and couldnt understand why in spite of everything appearing normal I was descending at an alarming rate. Of course everything was normal! (at least so far as the engine was concerned).

I had the same feeling. Checked full power, checked mixture was fully rich, checked Ts and Ps, checked RPM - all normal for full power, but WTF are we still descending?????:uhoh:

That was I think what really shook me about the whole thing.

[SparkyBoy]

What "mountains" were these? There are no mountains in the UK.

The dictionary defines a mountain as that which is ‘higher and steeper than a hill’. It is a landform that extends above the surrounding terrain in a limited area. Mountains usually have steep, sloping sides and sharp or slightly rounded ridges and peaks.
Generally, mountains are landforms that rise above 600 metres. Mountains exist on every continent and even beneath our great oceans.

Below a list of half of the English mountains and I don't have room on the forums for the amount of Scottish mountains (approx 750)

Scafell Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3001)97834BCentral and Western Fells89,90NY 215072Scafell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3002)96434BCentral and Western Fells89,90NY 206064Symonds Knott (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13001)95934BCentral and Western Fells89,90NY 207067Helvellyn (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3003)95034CEastern Fells90NY 341151Ill Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3004)93534BCentral and Western Fells89,90NY 223073Broad Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3005)93434BCentral and Western Fells89,90NY 218075Skiddaw (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3006)93134ANorthern Fells89,90NY 260290Helvellyn - Lower Man (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13002)92534CEastern Fells90NY 337155Great End (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3007)91034BCentral and Western Fells89,90NY 226084Bowfell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3008)90234BCentral and Western Fells89,90NY 244064Great Gable (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3009)89934BCentral and Western Fells89,90NY 211103Cross Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3010)89335AThe Northern Pennines91NY 687343Pillar (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3011)89234BCentral and Western Fells89,90NY 171120Nethermost Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13003)89134CEastern Fells90NY 343141Catstye Cam (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3012)89034CEastern Fells90NY 348158Esk Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3013)88534BCentral and Western Fells89,90NY 236075Raise (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3014)88334CEastern Fells90NY 342174Fairfield (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3015)87334CEastern Fells90NY 358117Blencathra (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3016)86834ANorthern Fells90NY 323277Bowfell North Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13004)86634BCentral and Western Fells89,90NY 245070Skiddaw - Little Man (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3017)86534ANorthern Fells89,90NY 266278White Side (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3018)86334CEastern Fells90NY 337166Striding Edge (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13005)86334CEastern Fells90NY 350149Crinkle Crags - Long Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3019)85934BCentral and Western Fells89,90NY 248048Dollywaggon Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3020)85834CEastern Fells90NY 345130Great Dodd (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3021)85734CEastern Fells90NY 342206Grasmoor (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3022)85234BCentral and Western Fells89,90NY 174203Gategill Fell Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13006)85134ANorthern Fells90NY 318274Great Dun Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3023)84835AThe Northern Pennines91NY 710321Atkinson Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13007)84534ANorthern Fells90NY 324282Stybarrow Dodd (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3024)84334CEastern Fells90NY 343189Little Dun Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3025)84235AThe Northern Pennines91NY 704330Scoat Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3026)84134BCentral and Western Fells89NY 159113St Sunday Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3027)84134CEastern Fells90NY 369134Crag Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3028)83934BCentral and Western Fells89,90NY 192203Crinkle Crags South Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3029)83434BCentral and Western Fells89,90NY 249045High Street (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3030)82834CEastern Fells90NY 440110Pillar - Black Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3031)82834BCentral and Western Fells89NY 166117Red Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3032)82634BCentral and Western Fells89NY 165106Hart Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3033)82234CEastern Fells90NY 368112Steeple (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13008)81934BCentral and Western Fells89NY 157116Shelter Crags (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3034)81534BCentral and Western Fells89,90NY 249053The Cheviot (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3035)81533The Scottish Border to the River Tyne74,75NT 909205High Stile (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3036)80734BCentral and Western Fells89,90NY 170148Lingmell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3037)80734BCentral and Western Fells89,90NY 209081The Old Man of Coniston (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3038)80334DSouthern Cumbria96,97SD 272978High Raise (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3039)80234CEastern Fells90NY 448134Kirk Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3040)80234BCentral and Western Fells89,90NY 194104Swirl How (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3041)80234DSouthern Cumbria89,90NY 272005Green Gable (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3042)80134BCentral and Western Fells89,90NY 214107Haycock (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3043)79734BCentral and Western Fells89NY 144107Brim Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13009)79634DSouthern Cumbria79NY 270985Green Side (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3044)79534CEastern Fells90NY 352187Knock Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3045)79435AThe Northern Pennines91NY 721302Dove Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3046)79234CEastern Fells90NY 374104Rampsgill Head (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3047)79234CEastern Fells90NY 442127Grisedale Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3048)79134BCentral and Western Fells89,90NY 198225Mickle Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3049)78835AThe Northern Pennines91,92NY 804243Kirk Fell East Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3050)78734BCentral and Western Fells89,90NY 199106Allen Crags (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3051)78534BCentral and Western Fells89,90NY 236085Great Carrs (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13010)78534DSouthern Cumbria89,90NY 270008Thornthwaite Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3052)78434CEastern Fells90NY 431100Glaramara (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3053)78334BCentral and Western Fells89,90NY 246104Kidsty Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13011)78034CEastern Fells90NY 447126Pillar Rock (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13012)78034BCentral and Western Fells89,90NY 171123Dow Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3054)77934DSouthern Cumbria96,97SD 262978Harter Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3055)77834CEastern Fells90NY 459092Red Screes (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3056)77634CEastern Fells90NY 396087Glaramara - Looking Steads (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13013)77534BCentral and Western Fells89,90NY 245101Shelter Crags North Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13014)77534BCentral and Western Fells89,90NY 249057Grey Friar (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3057)77334DSouthern Cumbria89,90NY 259003Sail (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3058)77334BCentral and Western Fells89,90NY 198202Wandope (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13015)77234BCentral and Western Fells89,90NY 188197Hopegill Head (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3059)77034BCentral and Western Fells89,90NY 185221Meldon Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3060)76735AThe Northern Pennines91NY 771290Great Rigg (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3061)76634CEastern Fells90NY 355104Stony Cove Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3062)76334CEastern Fells90NY 417100Wetherlam (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3063)76334DSouthern Cumbria89,90NY 288011High Raise (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3064)76234BCentral and Western Fells89,90NY 280095Ill Bell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3065)75734CEastern Fells90NY 436077Hart Side (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13016)75634CEastern Fells90NY 358197Sand Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13017)75634BCentral and Western Fells89,90NY 187218Red Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3066)75534BCentral and Western Fells89NY 160154Dale Head (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3067)75334BCentral and Western Fells89,90NY 223153Little Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3068)74835AThe Northern Pennines91NY 781224Burnhope Seat (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3069)74735AThe Northern Pennines91NY 785375Carl Side (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3070)74634ANorthern Fells89,90NY 254280Black Sails (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3071)74534DSouthern Cumbria89,90NY 282007High Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3072)74434BCentral and Western Fells89,90NY 180140Round How (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13018)74134BCentral and Western Fells89,90NY 218081Little Stand (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13019)74034BCentral and Western Fells89,90NY 250034Hobcarton Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3073)73934BCentral and Western Fells89,90NY 194220Robinson (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3074)73734BCentral and Western Fells89,90NY 201168Harrison Stickle (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3075)73634BCentral and Western Fells89,90NY 281073Seat Sandal (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3076)73634CEastern Fells90NY 343115Whernside (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3077)73635BThe Central Pennines98SD 738814Combe Head (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13020)73534BCentral and Western Fells89,90NY 249109Long Side (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3078)73434ANorthern Fells89,90NY 248284Little Gowder Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13021)73334BCentral and Western Fells89NY 140109Kentmere Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3079)73034CEastern Fells90NY 465077Codale Head (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13022)73034BCentral and Western Fells89,90NY 289090Hindscarth (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3080)72734BCentral and Western Fells89,90NY 215165Clough Head (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3081)72634CEastern Fells90NY 333225Ullscarf (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3082)72634BCentral and Western Fells89,90NY 291121Ingleborough (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3083)72435BThe Central Pennines98SD 740745Thunacar Knott (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13023)72334BCentral and Western Fells89,90NY 279080Glaramara South Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3084)72134BCentral and Western Fells89,90NY 242097Froswick (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3085)72034CEastern Fells90NY 435085Whiteside (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3086)71934BCentral and Western Fells89,90NY 175221Birkhouse Moor (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13024)71834CEastern Fells90NY 363159Harwood Common (Redgleam) (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13025)71835AThe Northern Pennines91NY 795363Great Shunner Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3087)71635AThe Northern Pennines98SD 848973Brandreth (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3088)71534BCentral and Western Fells89,90NY 214119Lonscale Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3089)71534ANorthern Fells89,90NY 285271Hedgehope Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3090)71433The Scottish Border to the River Tyne80NT 943197Branstree (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3091)71334CEastern Fells90NY 477100Dead Stones (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3092)71035AThe Northern Pennines91NY 793399Knott (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3093)71034ANorthern Fells89,90NY 296329High Seat (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3094)70935AThe Northern Pennines91,92NY 802012Melmerby Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3095)70935AThe Northern Pennines91NY 652380Pike of Stickle (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3096)70934BCentral and Western Fells89,90NY 273073Great Stony Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3097)70835AThe Northern Pennines91,92NY 823359Wild Boar Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3098)70835AThe Northern Pennines98SD 758988Whiteside West Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13026)70734BCentral and Western Fells89,90NY 170219Yoke (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3099)70634CEastern Fells90NY 437067Pike of Blisco (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3100)70534BCentral and Western Fells89,90NY 271042Great Whernside (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3101)70435BThe Central Pennines98SE 001739Chapelfell Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3102)70335AThe Northern Pennines91,92NY 875346Ladyside Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3103)70334BCentral and Western Fells89,90NY 184227Middleboot Knotts (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13027)70334BCentral and Western Fells89,90NY 213080Bowscale Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3104)70234ANorthern Fells90NY 333305Buckden Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3105)70235BThe Central Pennines98SD 960787Cold Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3106)70134BCentral and Western Fells89,90NY 262035Pavey Ark (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13028)70034BCentral and Western Fells89,90NY 284079Backstone Edge (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13029)69935AThe Northern Pennines91NY 725277Gray Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13030)69934CEastern Fells90NY 428117Caw Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13031)69734BCentral and Western Fells89NY 131109Grey Knotts (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13032)69734BCentral and Western Fells89,90NY 217126Rest Dodd (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3107)69634CEastern Fells90NY 432136Fendrith Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13033)69635AThe Northern Pennines91,92NY 877333Great Knott (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13034)69634BCentral and Western Fells89,90NY 260043Archy Styrigg (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13035)69535AThe Northern Pennines91,92NY 802003Pen-y-ghent (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3108)69435BThe Central Pennines98SD 838733Seatallan (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3109)69334BCentral and Western Fells89NY 139083Great Calva (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3110)69034ANorthern Fells89,90NY 290311Hugh Seat (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13036)68935AThe Northern Pennines98SD 808991Great Coum (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3111)68735BThe Central Pennines98SD 700835Round Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3112)68635AThe Northern Pennines91NY 744361Allen Crags North Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13037)68434BCentral and Western Fells89,90NY 240092Bannerdale Crags (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3113)68334ANorthern Fells90NY 335290Cold Pike West Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13038)68334BCentral and Western Fells89,90NY 258035Swarth Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3114)68135AThe Northern Pennines98SD 755966Plover Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3115)68035BThe Central Pennines98SD 848752Loft Crag (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13039)68034BCentral and Western Fells89,90NY 277071Baugh Fell - Tarn Rigg Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3116)67835AThe Northern Pennines98SD 740916The Calf (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3117)67635AThe Northern Pennines98SD 667970Combe Door Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13040)67634BCentral and Western Fells89,90NY 253108Knoutberry Haw (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13041)67635AThe Northern Pennines98SD 731919James's Hill (Westernhope Moor) (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3118)67535AThe Northern Pennines91,92NY 923325Lovely Seat (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3119)67535AThe Northern Pennines98SD 879950Murton Fell (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3120)67535AThe Northern Pennines91NY 753246Sheffield Pike (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3121)67534CEastern Fells90NY 369181Calders (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3122)67435AThe Northern Pennines98SD 671960Killhope Law (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3123)67335AThe Northern Pennines86,87NY 819448Branstree East Top (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13042)67334CEastern Fells90NY 487103Wether Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=13043)67334CEastern Fells90NY 456167Great Knoutberry Hill (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3124)67235BThe Central Pennines98SD 788871Rogan's Seat (http://dbweb.liv.ac.uk/mountains/detail.asp?top=3125)

[possel]

Did a pre flight, took off by the time I was at 500 feet I saw all the clouds nearing in, next minute I was in the middle of the whole lot. It was as if someone put the duvet over the aircraft. Could not even see the prop in front of me, I was around 1000ft AGL,

I learned that one when doing my PPL. We were going to do some dual circuits and it looked just OK perhaps 800ft when pre-flighting. By the time we got to the end of the runway it had got worse as when I took off the cloudbase was nearer 400 ft. My instructor showed me how to do a low level circuit and we landed. He then said "I expected you to see how bad it was and decide to not take off, but thought I would let you learn for yourself!"

I certainly did - thanks Kev. Always best to learn when you have some experience on board rather than solo!

[wobble2plank]

Love this thread!!!!

Met and turbulence are major killers within the aviation industry and hobby. Be it viz, cloud, turbulence, hail or any other of the bizarre things that mother nature can throw at us.

As to the one about vertical flow can not force and aircraft into the ground, that one is a distinct killer! A fair few years ago I was piloting an 11 ton helo into a small island to pick up a casualty when we were caught by a monster up draught caused by the north atlantic winds striking the rather hilly mountain island (yes they were that strong!). I lowered the collective to reduce the rate of climb but to no avail, I was effectively in autorotation and climbing at 2000 fpm. Luckily it all died down by 2000' and I could sneak back in by going low over the ground. Whats the reason for this story? Reverse the flow, place it at low level and then add in the inertia of a mechanical object travelling toward the ground at 1000fpm plus. This is where air wins and we don't.

Turbulence is an interesting one, especially in mountainous terrain, hence the requirement for greater safety altitude separation. The demarkation line that seperates the smooth flow from the tubulent is no stationary. Rollers exist below and smooth flow above. This line is, however, greatly influenced by what is upwind of the ridge/hill/mountain that you are flying past.

Honesty and a willingness to learn will stand all of us in good stead.

Avoid cumulo granite, read the weather but more important UNDERSTAND IT!

:ok:

[Tuned In]

IO540

Why, if the pilot does not intend to use the GPS in the normal course of the flight, should it be switched on? Unless the pilot is so underconfidant that they would cancel the flight if it wasn't working then it is an extra, not an essential and they can wait for it to power up!

[wobble2plank]

Forgot to add...

I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation. Although I have to add that I also think, can't remember fully, that that is for IFR nav.

However, prudence says that if its fitted it would be useful to have it on and pre-programmed as a back-up! Especially as most units will 'hot-start' very quickly if switched on where they were switched off but can take up to 2 minutes if moved significantly from their last sattelite 'snapshot'.

Cheers

[IO540]

I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation. Although I have to add that I also think, can't remember fully, that that is for IFR nav

If you can find a reference for any of the above, a lot of people are going to learn a lot.

Fortunately it's all completely false; the product of internet pilot forums, UK aviation magazines printing any old rubbish, CAA publications which freely mix up personal opinion of some ex RAF retired navigator with law, sentiments from various people at CAA "safety" seminars, and PPL instructors who don't like students getting ahead of the syllabus.

[dublinpilot]

I was under the impression that GPS was not allowed to be used as a primary navigation aid and was only there as a backup to correct flight planning and VFR chart navigation.

You are under the wrong impression.

Having said that, what is primiary and secondary navigation is all very academic. In practice we then to use more than one method of navigation, and question them when they don't agree. Which one is primiary and which is secondary doesn't really come into it.

dp

[dublinpilot]

Why, if the pilot does not intend to use the GPS in the normal course of the flight, should it be switched on?

My answer to that would be, if they are considering it an emergency aid, then yes, turn it on and have it ready, so that it has a chance to acquire a fix, and will be available when needed.

If they don't consider it an emergency aid, then no. Forget about it, and when the workload increases in an emergency situation, leave the gps in the flight back, and work with what's available to you.

If things calm down.....such as if you had entered IMC, and then emerged into VMC on top....then by all means get it out. But when the chips are down, your having an inadvertent IMC encounter....that's not the time to be trying to find it, and having to start setting it up.

dp

[NudgingSteel]

I've only just chanced upon this thread and would like to add my tuppence-worth....
To the posters who think a downdraft can't force an aircraft to the ground: of course it can! It's exactly the same physics as windshear which still kills people. The moving air stream can change direction and speed extremely rapidly, whether due to an inversion, ground features etc. An aircraft has a certain mass, and therefore momentum, and therefore requires a certain amount of time to adjust its flight profile to match the new wind speed and direction it is operating within. Most people understand that windshear can be deadly if a rapid airspeed loss occurs near to the ground, since the aircraft may be unable to accelerate sufficiently to maintain flying speed. Why is it any different when an aircraft is descending rapidly towards the ground and is unable to accelerate rapidly enough in the vertical plane to avoid impact?
Another analagy might be when driving down the motorway, and there's a nice laminar airflow over your bonnet and windscreen. Light particles such as dust or smoke have so little mass and therefore can be easily lifted within the airstream over the car. Anything a bit heavier can't accelerate up so quickly, so insects mostly hit the screen instead of being flung over the car.
Which has caused me some work with a bucket and sponge these last few days......

[wobble2plank]

Fair enough, things have moved on since I last flew in a light aircraft :p

I seem to recall, also by re-reading my post, that I stated 'I was under the impression' hence putting forward that I wasn't 100% sure, so thanks for the venhement reply.

I do, however, have experience of GPS integrity warnings, RAIM (Receiver Autonomous Integrity Warning) outages and power failures.

The problem with GPS, and with every aid, is that it is just that, an aid to navigation. Albiet within RNAV IFR airspace it is essential, for VFR flying in VMC it is not. The total reliance upon a single piece of equipment for navigation is folly hence the CAA requirement to train without in order to instill the basics of clock, map, ground. This may seem archaic in the current technological climate but if it all goes wrong then at least the pilot can revert to the basics of map reading.

I disagree with those who see it as a piece of the devil kit destroying our pure aviation, seat of the pants capabilities but I do see a need to fly without it.

It is easier to fly with the basics of navigation under your belt and then revert to the assisted aids when needed, i.e. in times of emergency. Thus allowing the pilot to offload and gain situational awareness. There is also nothing wrong with student pilots getting ahead of the game and learning GPS theory and usage, just don't let it hinder the basic skills or, in the worst case, mask or overide them.

hope that clears my position up a little :E

[IO540]

These "GPS" debates always degenerate into the same arguments. I don't have a problem with any of this, but was suprised at some of the people who have jumped on me further back (who I happen to know are professional jet pilots, and they know what I do, and they should know better).

However, I don't think you quite meant to say

The problem with GPS, and with every aid, is that it is just that, an aid to navigation

If everything is no more than an aid to navigation, what do you actually navigate with then??

In your airliner you are totally dependent on an FMS with multiple INS inputs, with DME/DME corrections when you can get them. That's pretty good and anyway you would just ask for vectors if it all packed up. Or, if way out over the ocean, fly the current heading to the next WP, etc, but I doubt that has ever happened.

Flying VFR, you can be map reading with a compass and a stopwatch, but that is not 100% reliable either (far from it, as well all know!). Yet for some reason, map reading is some sacred ritual which can never go wrong, and everything else is just an "aid" to it.

[wobble2plank]

In your airliner you are totally dependent on an FMS with multiple INS inputs, with DME/DME corrections when you can get them. That's pretty good and anyway you would just ask for vectors if it all packed up. Or, if way out over the ocean, fly the current heading to the next WP, etc, but I doubt that has ever happened.



Hilarious,

Well done for finding the airbus nav fit. The FMGS is a good bit of kit that locks, freezes and is generally regarded as being over complicated. It also takes all inputs and outputs and promulgates them to the systems. The older systems don't use GPS as a primary system and therfore requires constant checks against radio nav aids. They are also reknowned for freezing, drop ontop an electrical failure and you have no ND or PFD and your back to an aeroplane.

If you can't see that flying an aircraft, VFR within VMC as many PPL pilots are required to do, without the reliance on GPS is important then what is? Up to this point the CAA has ensured that, at least within the check rides, the GPS is off, for good reason. Poor map reading needs to be identified and corrected. If you think that a PPL pilot should wander off on a nav leg without planning on a chart and following that then I despair, probably along with a large amount of people on these boards.

I think you will find that most, if not all professional pilots have all trained this way and have that fall back option. If not then lets type limit aircraft to GPS and non GPS fitted aircraft in the same way that the US seperates automatic and manual cars.

[chrisN]

Some corrections to the quotation that Mercenary Pilot showed:

The description is of a simple mountain wave system, as first identified by glider pilots years ago, with a simple airstream and mountain set up. Life in reality can be much more complicated.

I was in mountain wave last week with a windspeed at height of 17 knots. Some of us thought we detected some with only 10 knots.

Waves can be easily up to 45 degrees angled to the general wind direction, and some of my colleagues last week found it at approximately 90 degrees, i.e. up-and-down wind, not just across.

Interference patterns happen in wave. Herringbone cloud formations appear on satellite photos, just like interference in ripples on the surface of a flowing stream when going over more than one obstruction.

Hills and valleys channel winds into unpredictable local variations of wind direction and strength.

Some wave at low wind speeds has vertical components as high as the wind speed. Too complex to explain here, but in essence a streamline can be deflected vertically in a local area.

Vertical currents, up and down, can be encountered very close to the ground - certainly 1-200 feet and there have been cases of two windsocks on different parts of the airfield showing wildly different directions, even 180 degrees opposed. If caused by rotor, the wild, turbulent down draught can be very close to the ground - I have been towed through some.

Last week, while picking a field to land out in, I saw a wind pattern in a crop radiating outwards from a central spot - had to be a down burst reaching the ground and spreading out there. (Wind speed at the time was about 15 knots on the ground where I landed, 20 knots in the air.)

Chris N
=====================

[IO540]

Wobble, not sure I suggested anything that you have written in your last 2 paras.