Fancy buying our aircraft carrier satnav, Raytheon asks UK American defence firm Raytheon has said it is in talks with the Ministry of Defence to put the US Navy’s “satnav for F-35s” system onto new British carrier HMS Prince of Wales. The USN’s Joint Precision Approach and Landing System (JPALS) is already being integrated onto the service’s F-35Cs and the US Marine Corps’ F-35Bs – …
GPS is insufficiently precise for landing on anything, let alone a moving object on the high seas in potentially adversarial conditions. Specifically its vertical accuracy is quite poor, being at the best of times a multiple of the horizontal accuracy, and possibly way out due to GPS's assumption that the earth is flat.
This system, like many others (your local airport's ILS probably uses something similar), augments GPS with local reference measures, allowing far more precise positioning in all dimensions relative to the local reference (in this case the ship).
JPALS is a militarised version of this relatively common technology, with all the usual bells and whistles you'd expect to make it resistant to jamming and capable of working on a ship.
If GPS is useless then how did Harriers and a variety of Choppers land on all sorts of ships in the past eh?
I witnessed the first trials of Harriers landing on Ark Royal. Some of it was in pretty shitty weather.
Need GPS to land? Wusses. Find the ship yes but to land? Wusses
'If GPS is useless then how did Harriers and a variety of Choppers land on all sorts of ships in the past eh?'
By the pilots working very hard in some instances, e.g. poor weather. This system reduces the pilot workload, because why not* and if it can reduce the time taken to recover the aircraft it minimises the time the ship is on a predictable course**.
Having seen trials of the predecessor system on the VAAC Harrier landing on Invincible it's kind of like magic.
*I mean safety probably, the cost of training a pilot means you really don't want to lose them if you can help it.
**For the hard of thinking a predictable course makes it easier for the Opfor to generate a firing solution.
Just remember, sometimes, systems fail, even in the venerable Harrier. And yes, landing with just the airmanship of a relative novice on the aircraft.
After making a radio transmission and not receiving a response, Watson realised his radio wasn't working, and that his inertial navigation system hadn't taken him back to his expected location for landing.
...
"Well, I thought, in for a penny, in for a pound."
http://www.forces.net/news/tri-service/day-royal-navy-pilot-landed-spanish-container-ship
http://www.telegraph.co.uk/news/uknews/1553244/Why-lost-jet-pilot-took-ride-on-container-ship.html
"JPALS is a militarised version of this relatively common technology, with all the usual bells and whistles you'd expect to make it resistant to jamming and capable of working on a ship."
JPALS is a militarised version of this relatively common technology, with all the usual bells and whistles you'd expect to make it seventeen times more expensive, much later to arrive and not available when you actually need it.
There, FTFY.
>I witnessed the first trials of Harriers landing on Ark Royal
That's the beauty of the F35, by not having any carrier take off and landing capability a lot of stress on the airframe and pilots is reduced.
Our aircraft carriers will be perfectly able to carry aircraft around safely. A simple system of drawing chalk outlines around them when they are parked will allow them to be located to within inches
"That's the beauty of the F35, by not having any carrier take off and landing capability a lot of stress on the airframe and pilots is reduced."
Well, seeing as the UK has bought them primarily for use on our carriers, I hope you're wrong about that.
I assume you mean that the F-35B doesn't have to have the larger wings and landing gear and the arrester hook of the F-35C (the naval version), so it's a bit lighter that it might otherwise be. On the other hand, the F-35B has all of the added complexity and weight of it's VTOL system, and might still be slightly lighter than the C version, but can carry much less weight and fuel.
Really, the F-35B should have been a unique design, leaving the A and C versions free from having to share a basic airframe with an aircraft designed for a very different role.
>Well, seeing as the UK has bought them primarily for use on our carriers, I hope you're wrong about that.
These were the carriers without catapults with aircraft that couldn't take off vertically without melting the deck, with an arrester hook that didn't work and couldn't land verticaly with any fuel or weapons load ?
Even assuming you got enough of the software to work that the planes could fly at all
Not true for several reasons, you need to read up on Differential GPS. Remember that "jitter" is injected into Civilian GPS, and without specific encryption e.g the P-code you won't get accuracy above a few meters. The Military, has P-code encryption so gets very accurate GPS circa 10cm.
JPALS works off.....wait for it.... real-time differential correction of the Global Positioning System (GPS) signal specifically SRGPS (Shipboard Relative GPS). But clearly you know more about it than Raytheon, which has only been testing this system since 2001 and the ship board version since 2013 http://aviationweek.com/defense/us-navy-completes-another-round-jpals-testing
But the more significant issue is that GPS can be jammed and in any conflict zone of any moderately advanced country (read third world and above) GPS jamming will be a thing. Hopefully there are electronic steerable antenna's on the system to combat jamming.
You need to evidence/ reference that because The P-Code - Precision Code is fundamentally part of the carrier signal for military GPS - as it utilizes P(Y) where (Y) is the encryption. Commercial GPS satellites cannot use/ are not authorised to use the P(Y)-code, as this was fundamentally designed as a military only precision.
"JPALS works off.....wait for it.... real-time differential correction of the Global Positioning System"
Which is... wait for it... exactly what I said.
The US don't "inject jitter" into the civilian-accessible GPS signals, and haven't done so in a very long time (since at least 2000 - current satellites don't even have the feature available). The military and certain other paying users do get access to more accurate signals (e.g. ionosphere corrections), but the civilian signal isn't intentionally degraded. There's just less information to use to correct the signal.
The problem with using GPS in the vertical is two-fold, and isn't anything to do with corrections.
The first major error factor is that the optimal distribution of satellites for "vertical" positioning is different from the optimal distribution for "horizontal" positioning and both of those are different from the optimal position for signal strength/satellite visibility. GPS, as designed, optimises for "horizontal" positioning and satellite visibility before it does "vertical" positioning. This makes sense when you remember its original design purpose. Inherently, the vertical accuracy is just lower.
The second major error factor is the use of a mean sea level approximation ellipsoid for the 0 altitude within GPS. This has to be corrected to be referenced against a real geoid, which has to be further corrected against a real elevation map. This introduces a huge amount of error in the vertical plane, particularly as making those corrections requires a precise horizontal fix in the first place. Throw in the rolling and pitching of the ocean and you'd best hope your will is up to date if you're trying to use GPS for altitude measurements while landing a plane.
Why would JPALS be running off Civilian GPS? The whole purpose of Military GPS with P-code and (Y) encryption is to reduce susceptibility to Jamming (it's not a complete solution but it helps). But even if it did run off civilian Differential GPS, so what, it can use any base station for correction as the Ship itself can transmit it's own DGPS reference signal as a station Baseline HD, which can correct for the local MSL variance on the Geodetic. Non-issue.
Flat as in smooth, not flat as in two-dimensional. GPS is designed around the earth as an ellipsoid centred on the earth's centre of gravity. This has little to no relation to the actual shape of the earth, which is bumpy as all shit and influenced by the time of year, the time of month and indeed the time of day. When you're landing a plane at high speeds these centimetre-scale differences matter, hence the need for a centimetre-scale positioning assistance system to fix your position properly.
"I fear that you may have spelled "WGS84" incorrectly."
Quite, but not quite. And this is where things get Very Fun for GIS developers. WGS84 specifies both an ellipsoid (the flat approximation of the earth) and a geoid (the not-flat reflection of the earth's gravity). The difference between the two is anywhere up to 100m in either direction and the geoid has a resolution of something like 100km.
So even if you've corrected to local sea level within WGS84, what you're going to get is something up to 100m different from what you had previously, and is accurate only on average within 100km of your position. Oh, and it may still have absolutely no bearing on your distance from the ground because it's based on the gravitational field.
GIS: Not even once.
It's nothing like flat earth, but GPS does make assumptions about the shape of the planet which makes slight differences to the latitude and longitude readings.
The basic differential GPS idea will cover things such as that, but it means the ship will have to transmit some sort of signal. This doesn't need to be powerful, but there is no way around a transmission from ship to returning plane, just to get into visual range.
Most GPS error comes from variations of signal velocity in the atmosphere, and there is always going to be the "cocked-hat" known to old-style navigators. As an extra problem, a ship's deck is never going to be as stable as a concrete runway. With the ship moving, it can't be quite like the differential GPS sending an error signal that can be applied in the vicinity of a fixed location. What the ship would have to do would be to transmit its current GPS position, encrypted, and the incoming plane gets a very good relative position.
We've used systems, such as the AN/SPN 32, for an awfully long time with the same level of accuracy*, no GPS or TACAN involved. The neat feature of GPALS is the "stealth" aspect in its functionality. So, evaluate the relative costs for the value of that, if any.**
* - the last step in the alignment procedure for that "ancient yet venerable" AN/SPN-32 is to slightly detune it as otherwise it'll plant every aircraft's landing gear on exactly the same spot on the carrier's deck. Kinda harc on the deck. {I shit you not. }
** - doesn't really matter as the pilots have to be ordered at gun-point before they'll even turn it on. {same}
Don't you mean the Century of the Anchovy? We have just left the Century of the Fruitbat, after all
Sorry, couldn't resist. Doffs hat (grey Tilley today) to the late, great Sir Terry Pratchett.
Mine is the, ... oh, wait, I didn't bring a coat, far too hot for that today.
"Surely HMS Prince of Wales should be referred to as a 'he' and not a 'she'?"
Gender is just a convention, even in gendered languages. In French a soldier on duty is feminine (la sentinelle), in German girls are neuter, and in Russian all dogs and horses are feminine but cats can be either. So, actually, calling ships "she" regardless of name is in some ways more gender neutral than calling them it.
I may be old-fashioned, but isn't the convention to call the ships of one's nation (UK in this case) "she" and the ships of other nations "it"? "She is a beauty" about "Prince of Wales", but "It is a big and ugly chunk of metal" when talking of "Gerald Ford"? On this side of the pond, that is...
'he' and not a 'she'?
I can just stomach ships being referred to as 'she', due to the centuries of naval tradition (along with rum and sodomy etc.). But I hate it when people refer to non gendered objects as 'he' or 'she'. My former brother in law referred to his Vauxhall Cavalier as 'she'. And he, was a twat.
It is traditional for engineers to refer to 'engines' as she, possibly (and here I apologise in advance to the politically correct among us) because so many pieces of mechanical kit can be temperamental. Not to say that men can't be temperamental too.
This applies doubly so for watercraft.
Maybe.
But if they pay for this self-landing technology, you start to wonder why they bother with the meatsack at the sharp end of the aircraft. Auto-take off is already easy enough, flight-plan already largely in the hands of machines. All the weapons systems are computerised and operated by Fisher-Price buttons.
Ignoring that anything that MoD and BAES do between them is a disaster, they might as well put a fleet of Taranis on the carriers, and then we could avoid the mess of the F35.
'But if they pay for this self-landing technology, you start to wonder why they bother with the meatsack at the sharp end of the aircraft.'
The meatsack having to concentrate on flying the aircraft has always been an issue for the military, the more they have to concentrate on that the less capacity they have for the actual mission. Traditionally the military have spent lots of money selecting people who're very good at flying aircraft and then after several years training see about having them make tactical decisions at the same time. Consequently one of the highest wash out rates in training was on the Tactical Weapons part of the fast jet course, which came near the end*, just before converting onto an operational type.
So in essence the ideal military aircraft is so easy to fly the pilot doesn't have to think about it, freeing him up to deal with the sensors and manage the mission, which is the bit that differentiates military aviation from a flying club.
*You couldn't have it earlier because they couldn't fly the jet well enough.
the ideal military aircraft is so easy to fly the pilot doesn't have to think about it, freeing him up to deal with the sensors and manage the mission?
Since, in real world terms, his unassisted eyesight won't be up to the job of target identification, evaluation and weapons targeting even at low level, the pilot is entirely dependent upon the sensors. In turn, this indicates the aircraft should fly itself, the sensors relay the information to drone controllers somewhere air conditioned, safe and comfortable, and they control the mission. Fragging a bunch of tribals at 350 knots and 5,000 feet isn't exactly seeing the whites of their eyes, so we might as well get over this Magnificent Men in Their Flying Machines nonsense for fast jets.
' the sensors relay the information to drone controllers somewhere air conditioned, safe and comfortable, and they control the mission.'
I believe bandwidth starts to become a problem. At the moment we're at the point where we can't shift the decision making process off platform for anything more than a handful of aircraft in the same area*, and at the same time don't have the AI to do it on the platform. I'm sure one or other of those will change in the future but then in 20 years time we'll have fusion power.
*Predator etc. are great at orbiting at medium to high level dropping the odd precision weapon, but that assumes a permissive environment. Against a near peer opposition they'd probably be relegated to, well scrap.
No back doors needed for that as the government already knows what the data should contain and it’s certifiably used only by trustworthy people who are not children and therefore don’t need protecting.
It’s only when they are not privy to the conversation that they want in. Please think of the children here.
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Given what happened to the USS Fitzgerald last week. Not quite the same system, but whatever they used worked so well for seeing a 700 ft container ship coming off starboard, after all! I wonder if it was Raytheon designed?
Obviously something basic went wrong there with basic US Navy processes, but the question seems to come down to 'were the sailors on watch asleep' or 'did the fancy computer system that runs it crash and they were flying blind'?
That piece of aeronautical junk called the F35 still doesn't meet specifications even after they have been relaxed. So why is the UK buying them, let alone ordering accessories?
And the F35's don't really like steam-driven Catapult Bridles because it puts excessive strains on the air-frames. Bet the Russians don't have that problem. Naturally, Cameron went for different catapult drive systems (steam / magnetic) for the two new aircraft carriers he bought.
What's wrong with the Euro fighter?
And the Brits can't even maintain their F35's - that has gone to Italy.
Must be nice to have unlimited funds that you never worked for.
I'm afraid you are talking out your arse. The QE2 & PoW won't have catapults and the capability to be retrofitted with them was removed by penny pinchers in Thales & the MOD. It was the new EMALS system that was putting unexpected stress on the aircraft's fuselage (not just F35's) in testing. As far as I'm aware that problem has been fixed.
'Bet the Russians don't have that problem. '
Well no, they don't use catapults, they roll their conventional aircraft down the deck and off a ramp which is the worst worst option for carrier aviation as you significantly reduce the available payload.
Some 40 per cent larger by displacement than QE, the Ford is designed to support around 160 launches and recoveries per day.
That is 160 fully loaded launches off a catapult that can come home without getting read of fuel tanks and ordnance to be caught by the arrestor gear. In terms of bomb load, etc the ratio is significantly better than 108/160.
'That is 160 fully loaded launches off a catapult that can come home without getting read of fuel tanks and ordnance to be caught by the arrestor gear.'
Well the requirement for the F-35B was to recover with stores (I think all of the internal ones) and you don't need to jettison fuel tanks if they're empty. You might dump the fuel but occasionally airliners have to do that and, oddly enough, so do conventional carrier aircraft as they'll have a max landing weight based on the load the tail hook can take and the available settings on the arrestor wire. This generally doesn't allow for a landing with all the bombs and rockets still attached.
The reason being any navy dangerous enough to have real chances of sinking your carrier locating it by radio will know (sound, satellites) its location.
So this is either for interoperability with the us (that makes kind of sense.. but how much are we going to pay them for their benefit?) or it makes no sense at all.
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