Jets V Heli's

[Guzz]

Evening fellow Pruners,

I'm currently updating my tactics briefs for work, particularly my evasion training presentations. I want to engage the audience a little more rather than the "If he does A consider countering with B" boring waffle.

I was wondering if any of you fast and pointy jocks had any interesting tales about engaging helicopters you would care to share? What made it difficult? What made it easy? Were there any times you came off worse?

What about my RW colleagues? I've heard most of Evalu8ters dits (with the corresponding hands in the bar) but what about the rest of you? Any tales of daring deeds vs the fast jet community?

[4Greens]

What you always need is a gun.

[Marly Lite]

One in each door preferably, with 1:1 tracer

[chinook240]

"I've heard most of Evalu8ters dits"

Haven't we all!

[Tiger_mate]

Camouflage works, especially against trees as does terrain screening.

Harsh manouvres don't unless to evade an in progress specific attack due to sun glinting off the rotors.

A helicopter matching speed and direction of a motor vehicle is difficult to find with a doplar radar. So a Wessex doing 60 kts adjacent to a HGV travelling up the A66 could not be found by three Tornado F3 tasked to kill it.

Jets v heli 1v1 is fair, 2v1 not so fair, and a coordinated 3v1 is death waiting to happen.

There was a time when it was assumed a missile would not be wasted on a helicopter. Recent conflict suggests otherwise. It was widely believed that it would be a spontaneous guns attack on a target of opportunity without a second pass. However the Luftwaffe Alpha Jets were specifically trained as anti-Hind helicopter killers.

A helicopter crew efficiently watching his six is great, until the attack comes from above. There are never enough eyes out of the helicopter.

It was once trialled that helicopters carrying USL on a Brigade move would stop and (low) hover if attacked with the option to jettison and run if necessary. I believe this concept was never subsequently adopted as an SOP.

[Sun Who]

A helicopter with an alert, well trained crew, operating together, is hard to kill. If they also make themselves hard to find in the first place, a helicopter is a very hard target.
If your tasked with killing helicopters, invest effort in the FIND function and shoot early.

Sun.

[Guzz]

I like that Sun Who! Mind if I use that as a quote?

Thanks for the replies so far, keep em coming! Anyone ever tried evasion training at night? If so, how did this affect the price of fish? (I can hazard a guess!)

[Rosevidney1]

The Gazelle would have been virtually impossible to detect and the fast pointy guys burn fuel at an alarming rate down in the weeds where the Gazelle did its work. I was very happy to be flying them - especially when I found that nobody saw us when performing FAC. When invited into the back seat of Jaguars I was unable to see my squadron chums either.

[Courtney Mil]

Really?

If it's moving and not on the beam, it's a simple radar target. If it beams or slows down it's a more difficult radar target, but that's just the use of different modes and operator skill.

Oh, and despite the camouflage, they are not invisible.

As for kill, IR missile or gun. Nice big, slow target, can't chage its velocity vector too quickly (understand that the vector is pretty short- it can be moved, but for defeating a tracking solution, not enough). Yum.

[awaiting manoeuvrability comments with glee]

[Courtney Mil]

Rosevidney1, the Gazelle is not indectible, for loads of reasons.

I truly hope you don't think that the Jaguar was the cutting edge of air-to-air. Hopefully Gazelle aircrew would be happy in their blissful ignorance.

[fantom]

Jets V Heli's
I suggest you look at your spelling and punctuation.

"Jets Vs Helis" would be a start.

[Lima Juliet]

FJs vs Helos? I suspect you don't even need to use a weapon to hurt them! I can remember a F3 going over a Winnebago in RED FLAG at around 720KIAS and around 500-800ft AGL (the ground was about 7,000ft AMSL so the jet was doing about M1.15 around the edge of the overland supersonic area) - the supersonic shock wave dragged the Winnebago off of the road and rolled it over several times. A similar shock wave would wreak havoc with a helo and the blades would take a right pounding - also I remember a supersonic pass on an airborne Herc causing an overstress being registered on the Albert!

LJ :cool:

[Evalu8ter]

Chinook 240 - surely not all of them? :E

[chinook240]

2hrs 24 mins, not bad!

[DBTW]

Most modern fighter radars will pick up the rotor disc...these days, helos have nowhere to run and nowhere to hide if they are rotors turning.

[Arm out the window]

Not quite a FJ, maybe an MJ, but an Iroquois gunship was credited with a Macchi kill on an Aussie exercise quite a few years back, as the story goes - the Macchis were flying a repeated predictable path and the Huey sat in a concealed hover and had a crack at them as they flashed past.

[Evalu8ter]

DBTW,
It's down to the driver in each airframe and the terrain you fight in. I've been able to elude Typhoons, F3s & F15s etc far more often than not - often having to call the jet on visually to get the training for my stude. Watching an F3 QWI put an AMRAAM into a truck on the A1M was a particular favourite....we were 3km from the datum he called the kill on.....

That said, a non-RWR equipped RW being flown to poor TTPs will be akin to a sitting duck.

In short,don't believe everything in the brochure.

Leon, this tells a different story;

J-CATCH - Wikipedia, the free encyclopedia (http://en.m.wikipedia.org/wiki/J-CATCH)

I'll take 5:1 most days - the only jet that achieves parity is the A-10.....

[Alber Ratman]

The thread title had to drag this classic out.


https://www.youtube.com/watch?v=xu_leZE76VE

[HEDP]

As RW I find that as the FW are generally skylined and do not change direction too much then they are a relatively easy kill. It is just a shame we don't get to play much otherwise the point would be made.

[John Eacott]

Evening fellow Pruners,

I'm currently updating my tactics briefs for work, particularly my evasion training presentations. I want to engage the audience a little more rather than the "If he does A consider countering with B" boring waffle.

I was wondering if any of you fast and pointy jocks had any interesting tales about engaging helicopters you would care to share? What made it difficult? What made it easy? Were there any times you came off worse?

What about my RW colleagues? I've heard most of Evalu8ters dits (with the corresponding hands in the bar) but what about the rest of you? Any tales of daring deeds vs the fast jet community?

Hopefully not covered by previous dits, but back in the dark ages when Helicopter vs FJ tactics were first being considered, some very pertinent sighting issues came out which led to significant changes in our kit.

The FJ drivers were able to pick up the white helmets first, then the white gloves, then the yellow mae wests; all of which gave excellent targets to ensure the helicopter wasn't going anywhere after the first pass.

Following that we (eventually) got green helmets, green gloves and the Mk15 LSJ with the flame orange stole neatly hidden behind olive green. A bonus was that we could watch the dials and gauges without filtering out the reflection of the yellow mae west!

Another long range visual pick was a Wessex with an odd coloured blade, which stuck out like the proverbial dog's as it flickered when seen from above. This has led (in much later years) to rotor blade patterns developed for ops such as aerial fire fighting, where visibility in smoke and high intensity flying is a relatively important issue.

[VinRouge]

I have heard anecdotal dits about manoeuvre kills by flying over the rotor disc at very high speed.

Of course, the heli driver always has the option of putting down and running away!

Can't see much joy in being a heli driver in a 2v1 with fast air.

[itsnotthatbloodyhard]

I remember trying to explain in a debrief, many years ago, that pointing a Lynx door gun in the general direction of a FJ at 2000 yards range isn't really what we'd consider a valid kill. Sadly the well-known personage from the Lynx wasn't having a bar of it, and departed in a smug cloud of self-delusion.

Hopefully some of the RW kills being discussed here are a little more rigorous.:ok:

[Evalu8ter]

John,
Good point re the odd coloured blade. How we laughed when OC78 flying a Sea King with such a blade flew up and down the Stanley Rd in the Falklands as OC1435 spent an hour trying to find him in an F3......at least the Argentinians didn't plan to use Sea Kings against us!

VR,
2v1, quite simple - multiple eyes to hold padlock and provide warnings.
1v2 great fun in peacetime, relies on the FJ crews getting their timing right - agreed, would be far more challenging 'for real'.

The shockwave kill philosphy is interesting, but very difficult to set up. If you've got the set up right you may as well select A-G strafe.

Pointing & squirting with a GPMG at 2000 yds is not valid; 8-10 secs tracking M134 at less than 1000m may well achieve some hits due to sheer weight of fire. The J-CATCH stats were a combination of turret guns and IR AAMs.

[SimonK]

Done a fair bit of HvF teaching myself with both Evalu8ter and others and also had a backseat ride in a Hawk vs 2xChinooks.

Like Evalu8ter I had to regularly talk the jets on despite them having your exact track and distance from the bull.....the helicopters are very difficult to see if being flown correctly with good lookout and in a tactical way. We often had to talk them back on after the merge itself to get a good fight for the trainee, as with a good bit of terrain you could quickly get away if in something smaller like a Puma or Lynx.

From sitting in the back of a Hawk I thought it would be easy to see two big lumbering Chinooks, but it wasn't....it was bloody difficult for both of us even though we knew where they were and as soon as the formation split it was even harder. There was no way a single seat jet would have been able to down both (one even?) aircraft without a lot of luck on his part and a total lack of awareness/ability on the other side. I'm fairly sure a direct overflight at very high speed would cause all manner of trouble for the helo, but I'm also fairly sure that it would be a very difficult manoeuvre to pull off against an 'aware' target and there is huge scope for the jets to get it very wrong. Certainly the drivers I spoke to in my past life weren't particularly keen on doing it....or so they said :}

So I think any kill would be a lucky break for the jet driver with the helo crew thumb up bum doing other things. Probably whinging about JPA and the low quality of their bag rats. Probably. :E

[ShyTorque]

Having done a bit of fast jet v. my Puma, I wasn't too bothered about them. It was the thought of the Frogfoot that did.

Mind you, the USAF did manage to shoot down a couple of Blackhawk with their F-15s a couple of decades ago, killing all 26 persons on board.

But they were supposed to be on the same side, so I wouldn't have thought the Blackhawk pilots were expecting the threat from above. :(

[Lima Juliet]

A mate of mine had an Angolan helicopter kill he got in a SAAF Impala (Aermacchi 326) during the 'Border War' before he joined the RAF. He took great delight in telling the QWIs that when we were training for Op DENY FLIGHT.

Whilst we talk about difficulty to detect - on DENY FLIGHT I intercepted a HIP after a call from AWACS of a possible 'slow mover' and it was easy to find. Many of my buddies did the same as well. The most annoying thing was that by the time the CAOC had got their act in gear, the helicopters would 'land on' knowing that they were now protected by our restrictive ROE and wait for us to run low on gas and have to leave - at that point they would get airborne and be on their way again. I even heard reports of a helo crew getting out and sticking up 2 fingered salutes at the NATO jets circling overhead! Hanging around helicopters for any length of time whilst they are on the ground is also a bad idea in case they get a MANPADS out of the back!

Finally, in a shooting war, a helicopter (or helicopters) are not going to be high up on the list of things to shoot down (unless intel tells us it is a SF or enemy VIP flight). Bombers, fighter sweep, AWACS, tankers and other ISTAR assets are all going to be higher up on the list for strategic gain than helicopters; which tend to be knobbled only as a target of opportunity if able.

LJ

[Evalu8ter]

Leon,
I'd agree with your last para.

Difficulty to detect has an awful lot to do with camouflage, terrain and pilot skill. I spent a delightful hour in Appleby once against 2x F3s with an E-3 overhead. No valid BVR mx shots and the only merges were the ones I called the jets in on my exact position. Bear in mind the jets also knew my start/end points and my Towline. On the other hand, 1v2 overwater could be quite different......

As I said before, a non-RWR equipped helo with a crew untrained in air to air tactics (which, let's face it, is most RW crews worldwide) can present a simple target for a FJ. But a well equipped cab, with a well trained crew is another story.

[Tengah Type]

I have just chanced upon an article in the old magazine Royal Air Force Flying Review from December 1962. It tells of an encounter between an Avro Rota ( Cierva C30a Autogiro ) and a pair of Fw 190s. The Rota was finishing a Radar Calibration sortie for CHF Rye at 4000ft in the evening of 14 July 43 when it was bounced by the Fw 190s. After desperate evasive action, including exceeding Vne, it got away and landed safely. There is no claim it was the first FW/RW combat, but there can not have been many earlier.

[glad rag]

Yep! [pity it's not 1/1 tracer mind....]

ClEo2OfA2Zs

[Tourist]

Got to agree with Evaluator. Always seemed to be an awful lot of telling them where we were. I should point out that that was in a seaking!
In my Gazelle they really would be very unlikely to see me. We used to lose visual on each other in formation FFS!

I always hear a lot about how the radar will find us. Not convinced. Had an E3 and a Bagger have a go on one occasion and didn't see any of the package. 3 SK4, 2 merlin and one Gazelle. We were low, but not proper war low, not even close. Wartime with an air threat I'd be at 10ft. How do missiles work through trees?

With no cover I'd be very scared. In European countryside with any trees and terrain I'd be relatively comfortable. How do you hit me if I hide behind a hill/trees/buildings etc?

The Gazelle has very low thermal signature, it's small, it's sprightly and it has fantastic lookout.
Tricky target if prepared.

[Mogwi]

Think I am the only UK FJ driver to have done it for real: I Puma with wingtip vortices, one A109A gunship with 30mm and a further (landed) Puma with 30mm, all in the space of a couple of mins. I have also done a fair bit of fighter evasion when I used to fly Wessex. But don't tell my old mother - I told her I played piano in a brothel!

Details in my book "Hostile Skies" or PM me.

[MOSTAFA]

Damn if you'd have missed the 109 we'd have had another.

I seem to remember post FI, 3 BAS decided everybody had to learn a new skill, ex38'ish; fighter evasion or something like that? I could never quite understand the point of wanting to put on a nice little flying display prior to being blown out the sky! Albeit hiding in the weeds was pretty damn difficult down south.

[Pontius Navigator]

I heard an LGB through the rotor disk works quite well provided the helo is within the ground burst envelope.

[Evalu8ter]

Mogwi,
Indeed you are - and the point re non-RWR equipped, non-Trained crews are emphasised by your success. I use your engagement as a case study, would you mind a pm with some questions?

PN,
GW1 saw an F15 kill a hind with an LGB; at the speed/height they were at it outranged the AIM-9 and didn't have any issues looking down into the desert. I fought a pair of F15Es over the North Sea a few years back and after 45 minutes of trashing F2/F3/Guns they presented a slightly narrower spread and simulated releasing a pair of LGBs each at us. The debrief was 'we were sick of you getting away - it didn't matter which way you went you were in a frag envelope...'. Fair one, bang to rights.........

[Pontius Navigator]

trawshing F2/F3/Guns they presented a slightly narrower spread and simulated releasing a pair of LGBs each at us. The debrief was 'we were sick of you getting away - it didn't matter which way you went you were in a frag envelope...'. Fair one, bang to rights.........

Nah, they would have had to get a passing Bucc to help :)

[Herod]

I'm pretty sure there was another thread on this sometime last year. Perhaps a search will find it for you.

[Courtney Mil]

I hate to burst your bubble, Evalu8ter et Al, but I spent a few months chasing helicopters around Bosnia, same as Leon. A tricky target to find sometimes, but we never missed one. We weren't allowed to shoot them down, more's the pity, but we had plenty of valid opportunities.

I don't think you'll find you're as safe and indestructible as you seem to think.

[Evalu8ter]

Courtney,
And having often flown rings around F3s, Typhoons, Hawks, et al in the Falklands and the UK I would suggest you're, perhaps, not as good as you think you are....yes I've lost plenty of engagements, but 'won' far more and losing is essential to learning.

Read the posts - there's a big difference finding poorly equipped and poorly trained helo crews to finding those with some kit & trg. I would suggest it's the former you were chasing around the Balkans.

[Courtney Mil]

Just passing on my experience of the subject. Modern airborne weapons systems can deal with helicopters.

I would suggest you're not, perhaps, as good as you think you are

Didn't intend to touch such a raw nerve, but thank you for your kind words.

[O-P]

I'm with Courtney on this one.


In planned Helio affil the egg whisks were hard to engage. When it wasn't planned (ie TOO) they were rats in a barrel. The FI was/is the best play ground for Helio plunking.


During planned affil I would tell the Chopper WHERE and WHEN I planned to engage, the eggers would have all their eyes out ready to play. Unplanned, just easy meat.


LJ,


I think the last brief on "Blowing the bloody rotors off" was a 0.95M pass and a 7G pull in combat pwr....and the C-130 boom damage is pants, they'd been woofing around at LL and blamed it on the F3 (I was there! As was the F3 STANEVAL pilot)

[SimonK]

Well this deteriorated fast. Good old pprune.

You think a helo is an easy target and you are almost certainly right against a single one lumbering around at height over flat terrain, flown in a non-tactical manner with no crew experience of fighter evasion and/or an RWR. However, the reality of what all of us rotary guys seem to be saying is a western crew/formation trained in evasion, employing good lookout and flying tactically is another matter entirely. Having flown and taught HvF against all manner of pointy things over ten years the only aircraft that regularly seemed able to 'win' when it got into the merge was the AlphaJet. Finding us, would of course be a different matter entirely for the AJ.

What I don't think you might appreciate (no offence meant) is there is a big difference in a 2 or 3 crew Mi8 (generally flown medium level like a FW) with no RWR and no experience of HvF vs a modern helicopter with 3 or 4 crew employing good lookout techniques, tactical low flying, route selection, RWR and trained in HvF techniques etc etc.

So I don't think its anywhere near as 'easy' as some of you make out, which is all I think that Evalu8ter was saying. He and I worked hand in hand with your brethren for a very long time and my experience as previously outlined was backed up by the debriefs received from them both in the air and afterwards on the ground. Nobody is trying to point score here, just trying to explain our experiences, which in turn is as valid as your experiences.

Interesting to hear your experiences of actual intercepts in Bosnia if you are able to share the detail....ie height, speed, terrain.....what actually happened?

[Tourist]

OP

The Falklands terrain very much favours the jet as I'm sure you are aware.

No trees, no buildings, lots of areas with not much terrain to hide in and no roads filled with vehicles. Added to this you have generally epic viz.

Try Norway and you have rather less chance

As SimonK says, references to finding Hips flown non tactically are irrelevant. It's the equivalent to shooting down a Ryanair Boeing on the Dublin run vs shooting down a B1B. Both are big, but they are a very different proposition.

[chinook240]

Surely much of the UK/FI affil, where the FJ frequently has difficulty finding the RW, is flown without AWACS support. More than likely in FRY/Iraq it was made easier.

[Dominator2]

There is no doubt that there are many wise words written here. I spent over 20 years developing tactics for FJ to attack helos. I also flew on and lectured at a number of QHTI courses. There is no doubt that Helo Attack can be a very difficult task when flown against a small, camouflaged, very low and well flown aircraft. The deficiencies of High PRF radars against such targets are well known. Modern fighters should not have the same limitations against very low/slow targets.
The advent of Link 16 made a significant difference to the FJ capability when utilised correctly. An E3 Link picture could enhance this capability.
The F3OEU developed and used pairs tactics at night using NVGs, Link16 and ASRAAM. With all players "Lights Out" the balance swung in favour of the FJ. The ASRAAM could be used as a poor mans IRST and used to compliment the radar. Again, modern fighters with IRST and sensor fusion many of the old limitations have been removed.
The difficulty was that to be safe and proficient required Above Average skills AND a large allocation of time for currency. HQ 1Gp decided that the cost and time required for CR crews to be proficient were not worth the threat assessment.
Be there no doubt for rotary guys that the threat may not be a Hawk day VMC. The latest technology is available to most countries. If a rotary is deemed to be a high value target then it has a high risk of being detected and engaged in many theatres throughout the world.

[Courtney Mil]

OK, some more good words here, but I can tell you this. Helicopters are detectable by modern air-to-air radars and can be engaged with modern airborne weapons.

With respect, you guys may be confusing close-quarters evasion training with the real world. If you want a fighter to get tied up with you in a visual fight for training purposes and then believe that that's how it's going to be for real then good luck to you.

I mean no disrespect to the helo community whatsoever. I think the FJ guys -if you'll let them - would be a much better ally to you than you think. But, you shouldn't think that the fighters cannot find and kill you. Fortunately, and contrary to the tone from some of the helo guys here, RAF fighters are actually on your side.

[High_Expect]

Courtney.... Perhaps they're having flashbacks to their streaming during training?

[Evalu8ter]

Courtney,
Apologies if my tone is offensive to you but your reluctance to accept the experience of others is starting to get a little wearing. I've spent several hours with high class FJ drivers discussing and disecting our mutual tactics to mutual benefit, including flying several on the JS (most of whom were impressed by what we could do and became better at hunting us afterwards...) I'm sorry if my comments irk your ego, but you don 't seem to accept that anybody else has a valid opinion.

Of course RW are detectable by radars/mx, no-one ever said they weren't, but the helo (if properly equipped and trained) does have options & TTPs to defeat most BVR threats. Things change - ASRAAM caused us to rethink some tactics, but with help from the FJ community we tried some solutions. Likewise, I flew several sorties helping the typhoon to calibrate the radar and hone their TTPs when the OEU was standing up. Please don't assume we don't talk to RAF FJ crews - we do, a lot. Sorry I didn't get the chance to talk to you.

I can't expect you to understand what's happened in my cockpit during several hundred 'engagements' any more than I yours. I've had to play dumb for F3 convexees to take valid shots (before, at the request of the OCU staff, proving it's not easy..) and I 've also had to ask Typhoon guys to dumb their system down to better prepare my studes against the likely threat. It's called teamwork and it's really quite useful. That little part of 4/84 about sortie aims ......

In short, you haven't got a death ray and I haven't got a cloaking device....therefore kit, terrain and training make a difference.

HE - oh dear, weak reversionary banter......

[SimonK]

High_Expect Courtney.... Perhaps they're having flashbacks to their streaming during training?


Quality and most importantly, funny banter too :hmm:

Would you like fish with those chips sir? :}

[Guzz]

Gents,

Many thanks for the many replies, lots of great gen there to include in my future presentations and discussions on the topic. I'll send out a few PM's over the next week or so to some of you to expand on some points made if that's OK?

FWIW, my own experience of participating in, and instructing ET has been a very mixed bag. I have been taken apart by some very good FJ drivers, we have evaded with ease others. One Tiffie pilot managed to direct his wingman, give us running commentary of the effectiveness (or not!) of our formation manoeuvres, and effectively fight his own jet at the same time. Hats off to whoever that was!

On the other end of the scale, I've been up against Typhoon/Hawk/F3/Gripen pilots who, despite using the full capabilities of their aircraft against us, were unable to find us let alone successfully engage. This includes "on the towline" and bouncing us at unknown points on our route.

I guess it all comes down to man over machine?

Guzz.

[Turbine D]

I've been up against Typhoon/Hawk/F3/Gripen pilots who, despite using the full capabilities of their aircraft against us, were unable to find us let alone successfully engage.
Well, that is about to end (sooner or later), no more hiding. := ;)

F-35 pilots to wear $400,000 helmets that can see through the plane | Fox News (http://www.foxnews.com/tech/2015/04/02/f-35-pilots-to-wear-400000-helmets-that-can-see-through-plane/?intcmp=sem_outloud)

[O-P]

Evalu8ter.

I don't believe that Helio affil was ever part of the F3 OCU syllabus. It was included in the QWI cse, for a while, then ditched.


Tourist.


The terrain in the Gulf is very like that of the FI, no trees, traffic, buildings etc (OK, it's different colour). I haven't been to war in Norway.


O-P

[Tourist]

OP

Do you think that the helicopters tend to hang around the empty bits of the gulf?

It's funny, because I seem to remember lots of buildings trees etc around the gulf, in fact if I look out my window, I am surrounded by a sprawling endless city. Lot like he rest of the peopled areas of the gulf really. Afghan obviously gets to have terrain as well.

[Mick Strigg]

Can I ask why tactics, which are "Confidential" at least and normally "Secret", are being discussed in this open forum, particularly by serving members of HM Forces?


This thread should be locked and deleted.


Poor Social Media discipline chaps!

[Tourist]

Oops.

We let the "go really low and hide behind sh1t" secret out of the bag....

[teeteringhead]

Oops.

We let the "go really low and hide behind sh1t" secret out of the bag.... so long as we never let them find out about the "land on and run away screaming" tactic....


.... oh b%gger ...... :ugh:

[sandiego89]

Mogwi: Think I am the only UK FJ driver to have done it for real: I Puma with wingtip vortices, one A109A gunship with 30mm and a further (landed) Puma with 30mm, all in the space of a couple of mins. I have also done a fair bit of fighter evasion when I used to fly Wessex. But don't tell my old mother - I told her I played piano in a brothel!

Details in my book "Hostile Skies" or PM me.

Mogwi/Dave, thank you for your great read in "Hostile Skies", I really got a lot out of the book. Superb, will have to pull it off my shelf again (for the upteenth time).

Perhaps from "Hostile Skies" or another read, another piece of advice for the helo driver wanting to avoid the FJ is to avoid flying above water as much as possible. The moving disk over water is much easier to pick out than it is over land.