Gnat vs. Hawk Flight Characteristics
Join Date: Jun 2007
Location: Petersfield
Age: 66
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
Clearly aeroplanes from different eras. Was the Gnat better suited as a lead in to early fast jets such as the Lightning, and the Hawk optimised as an introduction to later fighters such as the Tornado with fewer rough edges?
Gnome de PPRuNe
Join Date: Jan 2002
Location: Too close to Croydon for comfort
Age: 60
Posts: 12,618
Received 293 Likes
on
161 Posts
There's an airworthy single seater Hindustan-built Gnat (Ajeet?) at North Weald - pic on the Air Britain site...
The cockpit of the Gnat to which the OP refers has been butchered into bearing scant resemblance to any RAF Gnat...
The Gnat's OR946 instrument display and general characteristics made it an excellent lead-in trainer for the Lightning, although students would first have to complete their weapons course on the Hunter.
Hawk was intended to replace both Gnat and Hunter but had few, if any, swept-wing characteristics. But as a trainer it has served the RAF well - even though it lacks the Gnat's soul.
The Gnat's OR946 instrument display and general characteristics made it an excellent lead-in trainer for the Lightning, although students would first have to complete their weapons course on the Hunter.
Hawk was intended to replace both Gnat and Hunter but had few, if any, swept-wing characteristics. But as a trainer it has served the RAF well - even though it lacks the Gnat's soul.
Beagle
Re your post #6 above I am intrigued. It implies that you soloed on both the Gnat and the Hunter whilst at Valley so how come? As I recall, students generally did the Gnat course with the Hunter course on 3 Sqn being reserved for foreign nationals and those that were too big/long for the Gnat.
Re your post #6 above I am intrigued. It implies that you soloed on both the Gnat and the Hunter whilst at Valley so how come? As I recall, students generally did the Gnat course with the Hunter course on 3 Sqn being reserved for foreign nationals and those that were too big/long for the Gnat.
The original plan was as a Gnat (and Hunter T7) replacement as an advanced trainer - the switch to a primarily tactical attack aircraft led to Hawk and Alpha Jet to fulfil the trainer role
As there was usually a 'hold' between completing the Gnat course and starting at TWU, we were given a short Hunter refresher course of around 20 hrs at Valley before starting at Brawdy.
In my case, I finished my Gnat course on 4 Jun 1975, then had an interesting detachment to Wildenrath in July and August before my planned Hunter refresher course at the end of September. But after 3 sim trips I was told that someone else needed my slot, so I went back to hold with 2 Sqn 4FTS, scrounging 18 hours of sandbag time until my Hunter course recommenced in mid-November.
I went solo on the GT6 on 9th Dec, but the course was mainly dual so I only had 3 solo trips before it finished in early January. Then solo again at Brawdy in the F6A a couple of weeks later.
The long Hunter course was indeed mostly for foreign students and those too big to fit the Gnat, but the short Hunter refresher was for everyone except those creamed off to be Gnat QFIs.
In my case, I finished my Gnat course on 4 Jun 1975, then had an interesting detachment to Wildenrath in July and August before my planned Hunter refresher course at the end of September. But after 3 sim trips I was told that someone else needed my slot, so I went back to hold with 2 Sqn 4FTS, scrounging 18 hours of sandbag time until my Hunter course recommenced in mid-November.
I went solo on the GT6 on 9th Dec, but the course was mainly dual so I only had 3 solo trips before it finished in early January. Then solo again at Brawdy in the F6A a couple of weeks later.
The long Hunter course was indeed mostly for foreign students and those too big to fit the Gnat, but the short Hunter refresher was for everyone except those creamed off to be Gnat QFIs.
Some thread drift:
The removed section of flap vane on the Hawk cured the strong pitch down with flap, as discovered by Duncan Simpson on its first flight. As the removed section is outboard of the tailplane span, can anyone explain just how that works ?
Hawk, Gnat, you guys dont know what you missed ( fortunately) not flying the Vampire T11 !!!!!!
Probably the worst cockpit of any aeroplane I got to fly, in comparison the Gnat and Hawks were a dream !
My own limited experience of thse two types, suggest to me the Hawk was halfway between a JP 5 and the Gnat.
The removed section of flap vane on the Hawk cured the strong pitch down with flap, as discovered by Duncan Simpson on its first flight. As the removed section is outboard of the tailplane span, can anyone explain just how that works ?
Hawk, Gnat, you guys dont know what you missed ( fortunately) not flying the Vampire T11 !!!!!!
Probably the worst cockpit of any aeroplane I got to fly, in comparison the Gnat and Hawks were a dream !
My own limited experience of thse two types, suggest to me the Hawk was halfway between a JP 5 and the Gnat.
I had one trip in a Sea Vampire T22 back in 1969 - the cockpit was indeed rather an ergonomic slum! I recall one pre-start check was to make sure that instructor and student hadn't got their straps interconnected!
But we flew back from RNAS Lossiemouth to RNAS Yeovilton in little more time than it took me to get from RAF Kinloss to RNAS Lossiemouth as a passenger in what must have been one of the RAF's last Standard Vanguards!
But we flew back from RNAS Lossiemouth to RNAS Yeovilton in little more time than it took me to get from RAF Kinloss to RNAS Lossiemouth as a passenger in what must have been one of the RAF's last Standard Vanguards!
Where did they plan to use the Jaguar as a trainer? Was it planned as a Hunter replacement for TWU or after the Gnat?
When the first Gnats arrived at Valley I was a stude there on the Vampire. Echoing the comment above about the Gnat in a crosswind, I remember a bar conversation with one of the first Gnat QFIs. Having asked what the new bird was like, the answer was:
"Well, if you have let down through 30,000ft of cloud, seen the lights at minimums, and touched down in the middle of the runway on the crosswind limit, then in most aircraft your problems would be over. With a Gnat, they are just beginning."
I did have a ride in one at Rissy a few months later, and was impressed by its modernity compared with the Vampire T11. All a long time ago...……………..
Join Date: Aug 2014
Location: New Braunfels, TX
Age: 70
Posts: 1,954
Likes: 0
Received 0 Likes
on
0 Posts
I'm an A-4 driver with zero experience on Gnat and Hawk. Anyone out there with Gnat/Hawk and A-4 experience who could provide a comparison? I realize that the A-4 was twice the weight, wing area and thrust of the Gnat, but I'd be grateful for a comparison. Thanks.
I flew a Vampire T.11 many years ago. The cockpit was an ergonomic nightmare, but what sticks in my memory is how poor the initial acceleration was. I was pushing the throttle hard against the stop and even asked P1 if the brakes were dragging!
Below is an excerpt from an aerosociety.com article...
I have a feeling that the the 'Phantom Dive' IIRC did not occur on XX154 (1st Hawk) but on some of the subsequent A/C and came as a nasty surprise,but sorted fairly quickly by removal of the outer flap vane.
https://www.aerosociety.com/media/48...hawk-story.pdf
(1)....Stall behaviour The stall, as first experienced, occurred at a good low speed, but with very little buffet warning. One or other wing dropped suddenly and uncontrollably, though the aircraft did not depart into a spin and recovery was normal, rolling out to controlled flight. But clearly this was not acceptable. Flow visualisation revealed that a sudden ‘leading edge’ type of stall was occurring, originating at about mid-semispan. This was perhaps partly due to an aerodynamic concession, in that for production simplicity (and hence lower cost), the trailing edge flaps had been made with constant chord and section. But they were fitted to a fairly sharply tapered wing (taper ratio 0.34. tip to root) and so the ratio of flap chord to wing chord was at its highest at the outboard end of the flap and required too much of the flow at the local leading edge. Guided by work on the half model, the flap vane on the outer part of the flap was removed to detune it somewhat, at the cost of some maximum lift. Although the initial separation of the flow still occurred at the same point, the flow breakdown at the stall was kept from rapidly spreading towards the outer wing by the judicious positioning of a large fence. Buffet warning was obtained, at the cost of a little more maximum lift by putting triangular section “breaker strips” on the leading edges, inboard to give warning and outboard to give repeatability. As is related later, the outboard end of the flap vane was removed for another reason, and together with the devices above now gave acceptable behaviour, but lost about 5 knots of stalling speed. However, there was enough of a margin in maximum lift coefficient to meet the field performance requirements for the RAF. Clearly there was scope for much more fine tuning and investigation of more refined stall fixes, but there was a tight deadline to meet for the RAF, and this work was left to be done on the later developments.
(2) Phantom Dive ....It was first discovered when recovering from a stall with full flap and undercarriage up. It was found that at forward centre of gravity in that configuration, rapid fore-and-aft movement of the control column could induce an uncontrollable nose down pitch, with the nose down attitude and speed increasing quite rapidly. Recovery was straightforward, either by retracting the flap a few degrees, or by extending the undercarriage, but this was not acceptable as an operation, even though the configuration was unlikely to be used normally. It was dubbed the “Phantom Dive”. . It was shown with the half model of the Hawk at Hatfield that high local downwash at the tail,coupled with the very large nose down pitching moment induced by the flap, was causing the tailplane to stall on its lower surface, so that it could no longer provide adequate balancing power. It needed more lift, extended to higher angles of attack. A fixed slot with its associated drag was not an option on the Hawk although a cambered tailplane was tried on the model with some success.
Removal of the outboard vane of the flap reduced the flap pitching moment to such a value that the standard tailplane could cope, so this was the quick solution for the RAF.
Removal of the outboard vane of the flap reduced the flap pitching moment to such a value that the standard tailplane could cope, so this was the quick solution for the RAF.
Thank you, at last a sound explanation.
Got to agree with Ken Parry. When at CFS, the thought of sitting in the back of a Gnat, with its poor visibility, with a marginal student, on a filthy night with a cross wind at Mona, steered me to stay on the JP side !
Got to agree with Ken Parry. When at CFS, the thought of sitting in the back of a Gnat, with its poor visibility, with a marginal student, on a filthy night with a cross wind at Mona, steered me to stay on the JP side !
Very sensible staying on the JP's BA/BY -
The view from the back cockpit of the Hawk by comparison to the Gnat - well there is no comparison - from the back of a Hawk one could see the RWY right down to touchdown.
1st line - the Hawk T1 is a doddle to look after and (generally) very reliable,after I left the Air Force - I went to Zim to work on the Hawk T60 (as a civvy), I was based at Thornhill and once I had sorted out some long term problems (they did not have any Hawk experience)- most of my time could be spent drinking tea on the Hangar Veranda with an occasional 'work break' outside.
I even managed to get a Hawk ride including some spinning LOL (verboten for pax in the UK).
The view from the back cockpit of the Hawk by comparison to the Gnat - well there is no comparison - from the back of a Hawk one could see the RWY right down to touchdown.
1st line - the Hawk T1 is a doddle to look after and (generally) very reliable,after I left the Air Force - I went to Zim to work on the Hawk T60 (as a civvy), I was based at Thornhill and once I had sorted out some long term problems (they did not have any Hawk experience)- most of my time could be spent drinking tea on the Hangar Veranda with an occasional 'work break' outside.
I even managed to get a Hawk ride including some spinning LOL (verboten for pax in the UK).
KenV - I have flown all three.
My Hawk time is very limited - but I found it an easy aircraft to fly and very forgiving. The view from the rear is great for a trainer, but because the rear cockpit is raised above the rolling axis of the aircraft, it is slightly uncomfortable in a dynamic ACT sortie where there is lots of rolling under "g". Very easy to fall over when getting out at the end of the sortie! But a good trainer, albeit not good at instilling some of the important aspects of flying such as landing on speed on the numbers. Too forgiving!
The Gnat was an absolute delight to fly, as others have said. Very quick, and very responsive. Tiny jet which you strapped on, rather than in. But it was a trainer and carried no external stores - other than semi-embedded "slipper" tanks for fuel. A great trainer but a dreadful view from the rear cockpit. However, I think that all who flew it loved it.
The Scooter (I flew the A-4M, so it had the big engine - P408?) was as delightful as the Gnat in many ways with a similarly small cockpit which you strapped on. I never flew a clean-wing A-4, but it's load carrying ability was remarkable for such a small aircraft and it performed supremely well even when loaded. It was very close to the responsiveness of the Gnat - but those aerodynamic full leading edge slats which could deploy asymmetrically at times when pulling "g"and rolling in a dynamic ACT setting was disconcerting to say the least, and the cause of the odd headache! I loved the A-4M - however, the TA-4 with the P6 or P8 engine - you can keep!!
If offered the choice of which to fly one more sortie in - I'd go for the A-4M - simply because you could do so much more in it. If it had to be a two-seater, then the Gnat wins without question.
My Hawk time is very limited - but I found it an easy aircraft to fly and very forgiving. The view from the rear is great for a trainer, but because the rear cockpit is raised above the rolling axis of the aircraft, it is slightly uncomfortable in a dynamic ACT sortie where there is lots of rolling under "g". Very easy to fall over when getting out at the end of the sortie! But a good trainer, albeit not good at instilling some of the important aspects of flying such as landing on speed on the numbers. Too forgiving!
The Gnat was an absolute delight to fly, as others have said. Very quick, and very responsive. Tiny jet which you strapped on, rather than in. But it was a trainer and carried no external stores - other than semi-embedded "slipper" tanks for fuel. A great trainer but a dreadful view from the rear cockpit. However, I think that all who flew it loved it.
The Scooter (I flew the A-4M, so it had the big engine - P408?) was as delightful as the Gnat in many ways with a similarly small cockpit which you strapped on. I never flew a clean-wing A-4, but it's load carrying ability was remarkable for such a small aircraft and it performed supremely well even when loaded. It was very close to the responsiveness of the Gnat - but those aerodynamic full leading edge slats which could deploy asymmetrically at times when pulling "g"and rolling in a dynamic ACT setting was disconcerting to say the least, and the cause of the odd headache! I loved the A-4M - however, the TA-4 with the P6 or P8 engine - you can keep!!
If offered the choice of which to fly one more sortie in - I'd go for the A-4M - simply because you could do so much more in it. If it had to be a two-seater, then the Gnat wins without question.