F-5B runway length ??
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F-5B runway length ??
Wondering if someone could give me a workable runway length...for an F-5B, non ordinace loaded plane. (with and without chute if you know that as well).
Just a ball park...thanks.
Chutedragger.
Just a ball park...thanks.
Chutedragger.
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I think, and don't quote me, that it was somewhere around about 500 metres (1,500 feet). This ignores T & P's along with load weight.
The Canadians, at some stage, increased the fore undercarriage leg to increase angle of attack of the mainplane. This reduced the take of distance required.
The Canadians, at some stage, increased the fore undercarriage leg to increase angle of attack of the mainplane. This reduced the take of distance required.
Last edited by hval; 20th Apr 2012 at 15:58. Reason: Additional data
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T-38 was 4,000 feet to 7,500 feet for landing and around 2,300 feet to take off.
F-5B and T-38 have different aerofoils. Aerofoils!! Who ever uses that in normal speach. What I should have written was that they have different wings and the F-5B had/ has leading edge slats and trailing edge flaps.
Found some details..
Takeoff run for F-5B was 2200 feet with two Sidewinder missiles. Landing run from 50 feet with braking parachute was 3800 feet
Quote from Thornton Aircraft "Take-off and landing performance of the F-5 is superior to that of the T-38 due to the drag chute and larger wheels and brakes of the F-5. In addition, the F-5 exhibits less buffet in the traffic pattern due to its leading edge flaps."
F-5B and T-38 have different aerofoils. Aerofoils!! Who ever uses that in normal speach. What I should have written was that they have different wings and the F-5B had/ has leading edge slats and trailing edge flaps.
Found some details..
Takeoff run for F-5B was 2200 feet with two Sidewinder missiles. Landing run from 50 feet with braking parachute was 3800 feet
Quote from Thornton Aircraft "Take-off and landing performance of the F-5 is superior to that of the T-38 due to the drag chute and larger wheels and brakes of the F-5. In addition, the F-5 exhibits less buffet in the traffic pattern due to its leading edge flaps."
Last edited by hval; 20th Apr 2012 at 16:25. Reason: Found some additional data
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Having looked at the USAF - 1 for the type I would strongly consider a mimimum of 5,000' at the lightest weight at sea level and mild temperatures for take -off, and a healthy margin above that for landing on a dry runway. Touchdown speed is 135 kts.
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OK465,
Smoke the weed and be soooooo relaxed. (said in a smooth, calm, slow voice; like Marlborough man).
The above is an attempt at humour. A poor attempt, I know.
I guess it really depends on how relaxed you want to be
The above is an attempt at humour. A poor attempt, I know.
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How different are the wings?
I flew T38 - you fly the final turn in the pre-stall buffet and a careful eye on the AOA gauge. 155kts + fuel was approach speed....A heavyweight landing would have you coming in at 205/185!!
The "velocity squared" portion of the equation is pretty significant as far as energy to dissipate goes. Saw several smoke brakes, take barriers, and even an ejection as it departed the runway...almost all down to botched landings, not malfunctions.
I flew T38 - you fly the final turn in the pre-stall buffet and a careful eye on the AOA gauge. 155kts + fuel was approach speed....A heavyweight landing would have you coming in at 205/185!!
The "velocity squared" portion of the equation is pretty significant as far as energy to dissipate goes. Saw several smoke brakes, take barriers, and even an ejection as it departed the runway...almost all down to botched landings, not malfunctions.
The Canadians, at some stage, increased the fore undercarriage leg to increase angle of attack of the mainplane. This reduced the take of distance required.
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Ummmm... remember the RN lengthening the nose gear leg on its Phantoms to lower the take-off speed to deal with their catapults' lower end speed at weight?
And all the Scimitars, Buccaneers, and so on that had their tails tied towd when on the catapult so that their nose wheels were feet above the deck?
Apparently it works for Brit-built aircraft (and Brit-modified US-built aircraft). why wouldn't it work for Canadian-modified US-built aircraft?
And all the Scimitars, Buccaneers, and so on that had their tails tied towd when on the catapult so that their nose wheels were feet above the deck?
Apparently it works for Brit-built aircraft (and Brit-modified US-built aircraft). why wouldn't it work for Canadian-modified US-built aircraft?
Last edited by GreenKnight121; 22nd Apr 2012 at 08:20.
Raising the angle of attack works with carrier-launched aircraft because the catapult assists the aircraft to a speed equivalent to Vr within the length of the carrier, so the induced drag on the take-off run is irrelevant. Carrier aircraft can therefore have undercarriage arranged so that the aircraft has a positive AoA on the ground, and the pilot does not have to rotate the aircraft at Vr.
Land-based aircraft have to rely on their own power to reach Vr and so any unnecessary drag on the take-off run just increases TODR. Hence land-based aircraft begin have undercarriage arranged so that the aircraft has low (if not zero) AoA during the take-off run, and the pilot has to rotate the aircraft at Vr.
This is one of the reasons that carrier aircraft often have poorer take-off performance when operating from land than their land-based cousins. Also it was one reason that (as you point out) the RN launched the Bucc and Scimitar with their tails tied down - the aircraft was launched at rotation AoA from carriers without having to lengthen the nosewheel leg which would have penalised take-off performance when operating from land.
I'm thus very surprised that the Canadian's found that increasing the length of the nosewheel leg on their F5s improved take-off performance.
Land-based aircraft have to rely on their own power to reach Vr and so any unnecessary drag on the take-off run just increases TODR. Hence land-based aircraft begin have undercarriage arranged so that the aircraft has low (if not zero) AoA during the take-off run, and the pilot has to rotate the aircraft at Vr.
This is one of the reasons that carrier aircraft often have poorer take-off performance when operating from land than their land-based cousins. Also it was one reason that (as you point out) the RN launched the Bucc and Scimitar with their tails tied down - the aircraft was launched at rotation AoA from carriers without having to lengthen the nosewheel leg which would have penalised take-off performance when operating from land.
I'm thus very surprised that the Canadian's found that increasing the length of the nosewheel leg on their F5s improved take-off performance.
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GK wouldn't the cataput on the carrier aircraft overcome any drag issue?
I'm guessing that generally aircraft are configured to present the minimum drag during take off until the required speed is achieved. I see where Trim is coming from, the F-5 has no other thrust except engines so if they made it nose high the AoA increase should increase drag. What are we missing because they did it so it must have worked, does excessive engine thrust change things?
(Posted before I saw Trim Stabs last post, however I'm not saying it didn't work
)
I'm guessing that generally aircraft are configured to present the minimum drag during take off until the required speed is achieved. I see where Trim is coming from, the F-5 has no other thrust except engines so if they made it nose high the AoA increase should increase drag. What are we missing because they did it so it must have worked, does excessive engine thrust change things?
(Posted before I saw Trim Stabs last post, however I'm not saying it didn't work
)
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Extendable Nose Wheel Leg
The Canadian-built Freedom Fighter was referred to as CF-5A to distinguish it from Northrop-built machines. The two-seat version was known as CF-5D (D standing for "dual") rather than B.
The aircraft was to be powered by J85 engines built by Orenda. The Orenda J85s were of greater thrust than their US-built counterparts. The Canadian-built Orenda J85-CAN-15 engines were rated at 4300 lb.s.t. with after burning, as compared to only 4080 lb.s.t. for the J85-GE-13s which powered most F-5As and Bs. The increased thrust enabled the CF-5 to have a better speed and climb rate than that of the Northrop F-5A. Notably, initial climb rate was increased from 28,000 to 33,000 feet per minute.
The CF-5A introduced several refinements that resulted from USAF experience in Vietnam. The lengthy takeoff distances required at high weights were reduced by 25 percent by introducing a two-position extendable nose wheel leg, which increased the angle of attack during initial rollout by three degrees.
The aircraft was to be powered by J85 engines built by Orenda. The Orenda J85s were of greater thrust than their US-built counterparts. The Canadian-built Orenda J85-CAN-15 engines were rated at 4300 lb.s.t. with after burning, as compared to only 4080 lb.s.t. for the J85-GE-13s which powered most F-5As and Bs. The increased thrust enabled the CF-5 to have a better speed and climb rate than that of the Northrop F-5A. Notably, initial climb rate was increased from 28,000 to 33,000 feet per minute.
The CF-5A introduced several refinements that resulted from USAF experience in Vietnam. The lengthy takeoff distances required at high weights were reduced by 25 percent by introducing a two-position extendable nose wheel leg, which increased the angle of attack during initial rollout by three degrees.
I'm not denying it was true - just curious for an explanation.
There must have been a reason unique to the aircraft configuration and power, otherwise all aircraft would have adopted the same trick!
Perhaps the thrustline was slightly above CoG so that (in the original configuration) the aircraft pitched slightly nose down during the take-off run, resulting in negative incidence and additional drag. When the Canadians added yet more power, this problem may have been exacerbated to the extent that they worked out what was wrong and corrected the problem with a longer nosewheel leg. Just a theory.
There must have been a reason unique to the aircraft configuration and power, otherwise all aircraft would have adopted the same trick!
Perhaps the thrustline was slightly above CoG so that (in the original configuration) the aircraft pitched slightly nose down during the take-off run, resulting in negative incidence and additional drag. When the Canadians added yet more power, this problem may have been exacerbated to the extent that they worked out what was wrong and corrected the problem with a longer nosewheel leg. Just a theory.
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F5 and T-38 Wing Differences
US Herk,
The wings differed between the T-38 and the F-5 in the following ways: -
1/ The wing of the T-38 meets the fuselage straight and ends square (refer to page 10 of this linked document. Ignore the wing fences. The F5 wings do not; they have leading edge root extensions. See Here
2/ The F-5 has leading edge root extensions and wingtip launch rails for missiles. The LERX help at high alpha with stall speeds.
3/ the T-38 wing is constructed of honeycomb material while the wing of the F-5 family uses conventional skin over underlying support structure
The wings differed between the T-38 and the F-5 in the following ways: -
1/ The wing of the T-38 meets the fuselage straight and ends square (refer to page 10 of this linked document. Ignore the wing fences. The F5 wings do not; they have leading edge root extensions. See Here
2/ The F-5 has leading edge root extensions and wingtip launch rails for missiles. The LERX help at high alpha with stall speeds.
3/ the T-38 wing is constructed of honeycomb material while the wing of the F-5 family uses conventional skin over underlying support structure
Last edited by hval; 21st Apr 2012 at 09:59. Reason: LERX
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My only experience is with the F5 E & RF5 versions flying from 10000ft runways and on several occasions that wasn't long enough. I can remember 3 Barrier engagements and numerous over run cable traps.
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AGS Man,
Were the aircraft fully laden and flights carried out in hot climates?
If I remember correctly, the F-5E and RF-5 did have improved engines, but the weight increases did not match up to the improved engine performances. Did the F-5E also not have degraded aerodynamics due to all the external additions as well, when compared to the original F-5 and F-5B?
Were the aircraft fully laden and flights carried out in hot climates?
If I remember correctly, the F-5E and RF-5 did have improved engines, but the weight increases did not match up to the improved engine performances. Did the F-5E also not have degraded aerodynamics due to all the external additions as well, when compared to the original F-5 and F-5B?
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Trim Stab,
The CF-5 take of distance was 20% less than the US F-5.
I shall carry out some research later. I was wondering if the F-5 had neutral alpha and the CF-5 ended up with positive alpha when sat normally on the ground. In my head this is how I see the F-5 sitting. It may be a false memory.
By the way, I do know that many modifications made to the F-5 models built by Northrop came about because of the Canadian CF-5's and the Netherlands requirements (who bought some modified CF-5's from the Canadians).
The CF-5 take of distance was 20% less than the US F-5.
I shall carry out some research later. I was wondering if the F-5 had neutral alpha and the CF-5 ended up with positive alpha when sat normally on the ground. In my head this is how I see the F-5 sitting. It may be a false memory.
By the way, I do know that many modifications made to the F-5 models built by Northrop came about because of the Canadian CF-5's and the Netherlands requirements (who bought some modified CF-5's from the Canadians).
hval - just re-read your post and saw that the extended leg was used only when aircraft operating at higher weights (presumably underwing ordnance). This would fit my theory, as the extra underslung weight would lower the CoG further, resulting in pitch down when power was applied.
Also, the aircraft has a relatively short wheel-base with a nosewheel situated a long way from the nose of the aircraft - this too would contribute to nose-down pitching on take-off run if the thrustline was higher than CoG.
Also, the aircraft has a relatively short wheel-base with a nosewheel situated a long way from the nose of the aircraft - this too would contribute to nose-down pitching on take-off run if the thrustline was higher than CoG.
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Trim Stab,
The nose wheel extension increased length by 33cm (13"). This gave the 3.1 to 3.4 degree AOA increase.
The US also incorporated this nose wheel change in to later F-5 models. If you read "F-5 Tigers Over Vietnam" by Anthony J. Tambini he describes the use of this nose wheel extension on the F-5E models that were delivered to Vietnam. See Page 29. He also mentions how the US Navy F-4Bs had the same solution and how the Crusader F-8 had the variable incident wing - all for the same reason.
The wing of the F-5E wing had 0 degree incidence (when referred to the wing reference line) when sat on the ground with no weapon load and without the nose wheel extended. The trailing edge appears to have a slightly negative AOA with reference to the ground in this position! About 1 degree.
By the way. What appears to be a good book about the F-5 (all models) is the Warbird Tech Series Volume 44 "Northrop F-5, F-20/ T-38"
The nose wheel extension increased length by 33cm (13"). This gave the 3.1 to 3.4 degree AOA increase.
The US also incorporated this nose wheel change in to later F-5 models. If you read "F-5 Tigers Over Vietnam" by Anthony J. Tambini he describes the use of this nose wheel extension on the F-5E models that were delivered to Vietnam. See Page 29. He also mentions how the US Navy F-4Bs had the same solution and how the Crusader F-8 had the variable incident wing - all for the same reason.
The wing of the F-5E wing had 0 degree incidence (when referred to the wing reference line) when sat on the ground with no weapon load and without the nose wheel extended. The trailing edge appears to have a slightly negative AOA with reference to the ground in this position! About 1 degree.
By the way. What appears to be a good book about the F-5 (all models) is the Warbird Tech Series Volume 44 "Northrop F-5, F-20/ T-38"
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A little geeking found this
at about 3min.
I was also thinking that it might be for the higher weight, I guess the with the increase in engine thrust Canada were hoping to carry more, especially as they would be using it as their primary fast jet. My PoF is quite basic but the more I think about it wouldn't any increase in weight affect all the undercaridge to the same extent, therefore no change in AoA.
Could it have been to do with the wing shape for take off with slats and some flap deployed giving a negative AoA without the boost?
I was also thinking that it might be for the higher weight, I guess the with the increase in engine thrust Canada were hoping to carry more, especially as they would be using it as their primary fast jet. My PoF is quite basic but the more I think about it wouldn't any increase in weight affect all the undercaridge to the same extent, therefore no change in AoA.
Could it have been to do with the wing shape for take off with slats and some flap deployed giving a negative AoA without the boost?
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Ivan Rogov,
Thank you for that. Even with zero load they extend the nose wheel.
An increase in engine weight would effect the main landing gear more as the engines are closer to the main landing gear. The weight difference between the two engines (J85-GE-13 and the Orenda built General Electric J85-15) would be minimal. Maybe the additional equipment added weight to the airframe.
Thank you for that. Even with zero load they extend the nose wheel.
An increase in engine weight would effect the main landing gear more as the engines are closer to the main landing gear. The weight difference between the two engines (J85-GE-13 and the Orenda built General Electric J85-15) would be minimal. Maybe the additional equipment added weight to the airframe.