Farewell to the Sea Harrier

[chrisrobsoar]

A few points, picked from some of the previous posts.

The FRS1 Sea Harrier is based on the GR1/GR3 Harrier I (an all metal aircraft), with a new nose, Blue Fox pulse radar and some changes to make it better suited for the maritime environment.

The FA2 had further changes to the nose and Blue Vixen Pulse-Doppler radar with lookdown capabilities. Three quarters of the aircraft were re-built FRS1s and I think 15 were new builds. These gave the Fleet the capability to engage aircraft carrying anti-ship missiles at long-range, using the AIM-120C AMRAAM.

A FA3 based on the Harrier II (a largely composite aircraft) was offered in the early 90s, but turned down for financial reasons.

Most of the FA2 airframes are 25 years old and were found to be suffering badly from corrosion. Essentially there were insufficient numbers of the remaining newer aircraft to provide a viable force.

The lack of performance in regions with high temperatures is interesting as we have just agreed to sell 8 FA2s to India and I think that they already operate about 50 Harriers.

Rather than just temperature it is probably the high humidity and the low density of the air, which results in poor performance (The classis Density-Altitude problem).

The GR7/GR9 have a limited short-range self-defence capability using Sidewinder AIM-9L missiles.

But without the assistance of land based aircraft and carrier borne aircraft from its allies, it does leave the RN exposed to long-range attacks.

Chris

 

[Gaenth]

Actually high humidity, and density of air helps Turbofans in general because it increases compressor efficiency and it can stuff more matter in the combustion chamber, simply put, they have more to bite and swallow, the more air it takes, the more power. Temperature is what really dulls their performance because hot air is harder to squeeze and move. I don't think Harriers had the same problem operating in the North or South Atlantic.

India may not be so open about the performance of their Harrier fleet, and given it's use it's not such a big concern, but they sure have that problem as well.

Yep, the article talks about an engine uprate only and yep the Harrier II Pegasus installed on FA.2s would have been enough, but modifications needed for both airframe and engine are probably close in cost and complexity to development of a Harrier II FA.3 which as Mark and Chris pointed was dropped because of cost anyway.

 

[rossfrb_1]

Excuse my ignorance regards the Harrier series of aircraft (Harrier, Sea Harrier, Harrier 2..) I really don't know that much about them or what differentiates them from each other. But I was wondering, are there any legs left in this design? Is there any scope for Harrier 2 (AV8B?) to be further modified to say a mark 3 model (whatever that may mean, more powerful engine/aesa radar...)? Just wondering if the UK has any options other than F-35B?
I'm guessing that there are no plans for a mark 3 Harrier, but could there be?

cheers
rb

 

[chrisrobsoar]

Actually high humidity, and density of air helps Turbofans in general because it increases compressor efficiency and it can stuff more matter in the combustion chamber, simply put, they have more to bite and swallow, the more air it takes, the more power. Temperature is what really dulls their performance because hot air is harder to squeeze and move.

There are two aspects to this problem, the performance of the wing and the performance of the engine.

The density of the air decreases with increase in temperature. The density of the air also decreases with increasing height.

There is an ISO Standard Atmosphere, a model that describes how the atmosphere should with altitude.

It starts at Mean Sea Level (msl) and assumes that the pressure will be 1013.25 hPa (same as millibars) and the surface temperature will be 15Deg C and the humidity will be 0%.

In the gulf the temperature is very high in the summer most of the time over 30deg C and the humidity is often close to 100%.

The density of the air governs the performance of the wing.

The idea of density-altitude is that the actual density of the air is compared with the model and the density-altitude is the altitude at which the model gives the same density as the recorded density.

The bottom line is that during the summer in the gulf the density-altitude can be 6,000ft, which is a shame because the max hover altitude for the Harrier 1 (FA2s) is about 5,800ft. Also because of the limited amount of cooling water carried the hover duration is about 40sec. If the wing does less the engine has to do more, which makes the transition from horizontal to vertical flight problematic.

The effect on the engine is a bit more difficult. Generally jets work better at height. Water injection (water-methanol) has been used on Turbo-Prop aircraft to increase power, but much of the gain is due to the cooling affect on the incoming air. Overall high temperatures reduce the performance of Turbofans and high humidity just confuses the engine management system.



http://wahiduddin.net/calc/density_altitude.htm

http://www.aerospaceweb.org/question/planes/q0123.shtml

http://www.iso.org/iso/en/CatalogueListPage.CatalogueList?COMMID=712&scopelist=

http://en.wikipedia.org/wiki/Standard_temperature_and_pressure

 

[Gaenth]

Now that's a much better explanation! Thanks for the links as well Chris.

Excuse my ignorance regards the Harrier series of aircraft (Harrier, Sea Harrier, Harrier 2..) I really don't know that much about them or what differentiates them from each other. But I was wondering, are there any legs left in this design? Is there any scope for Harrier 2 (AV8B?) to be further modified to say a mark 3 model (whatever that may mean, more powerful engine/aesa radar...)? Just wondering if the UK has any options other than F-35B?
I'm guessing that there are no plans for a mark 3 Harrier, but could there be?

cheers
rb

You may want to check this link for some Harrier background: http://www.harrier.org.uk/history/index.htm

I believe the design is being stretched on a cost-benefit basis, and as money isn't coming in we can only expect upgrades to avionics, systems and weapons specially integrating the new generation of smart bombs, but nothing too spectacular on the plane itself. They did a rather good job expanding Harrier I into Harrier II and they ended with a totally new aircraft, so further more radical changes are most likely unpractical. Now the Harrier customer list isn't that long anyway and most of the customers have already their eyes on F-35 but as you'll read in the link the Harrier III has actually been considered.