Naif al Hilali
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Following on from :
F-16 Ferry Range Analysis
https://defence.pk/threads/pakistan-f-16-discussions-2.15226/page-649#post-8906190
and
F-16 Combat Mission Radius Analysis
https://defence.pk/threads/pakistan-f-16-discussions-2.15226/page-649#post-8916212
I was going to post the analysis of the JF-17's ferry and combat ranges to the JF-17 Discussions thread, but that thread is infested with trolls and flamers.
If there are no objections, I would like to start by analyzing the ferry range of the JF-17 today, and we will attempt to see how it was designed to PAF requirements, after we are done with the combat range analysis later in the week, Insha'Allah.
To recap, please recall from the F-16 Ferry Range Analysis part:
"I have been working on an analysis of ferry and combat ranges for active fighter aircraft. The conclusion will seem to be that (except for a couple of outliers) these figures are mostly similar for most modern combat fighters/attack aircraft. Not surprising considering that, no matter from what country the planes originate, they are usually designed to broadly similar payload/performance/range requirements.
...
I started with the F-16 because it's charts are widely available and can be checked online. So, it will form a baseline for assumptions to be made when data are not fully available for other aircraft.
No classified information will be presented in the analysis and (for the sake of alarm-raisers) any country that might be interested in the figures will have more accurate data and much more (tactics and capabilities) already made available to them by the manufacturer. The F-16 has been demoed to just about everybody including India.
The figures have all been rounded after calculations to make them more readable (and the roundoffs adjusted, for the nitpickers, so that they add up and/or are consistent)."
Now on to the task at hand. There have been many conflicting statistics on the JF-17's combat ranges. Not surprising given that operational & environmental conditions, takeoff & reserves requirements, and the need to evade enemy defenses, all of these exclude the possibility of fixing a hard number to a mission radius figure. Please recall that for the F-16C examples we worked out, the combat radius ranged all the way between 65 and 670 nautical miles.
For most aircraft, the only hard constructor-claimed range estimate you can seriously consider is the ferry range. This is usually stated under very well-known standard conditions with the aircraft flying under optimum cruise conditions all the way from Point A to Point B, with a nearly standard landing reserve.
We have a very good figure of 1,880 nautical miles for the JF-17 with three external tanks that has been validated by its overseas deployments. After considering all the claimed estimates and data, I decided to form this as the basis of my JF-17 analysis. It gives us a baseline for the JF-17's subsonic-cruise fuel consumption that should serve us well later, Insha'Allah.
Recall for the F-16A's ferry range with three tanks, we calculated:
F-16A Block 15 Ferry Range (16,300 pounds Aircraft Empty Weight)
Internal Fuel + 300 Gallon Centerline + Two 370 Gallon Drop Tanks
33,000 pounds Takeoff Weight
14,000 pounds [7,800 liters] usable fuel
- 500 pounds taxi & takeoff
- 800 pounds climbout to 36,000 feet initial cruising altitude, covering 60 nautical miles
- 11,700 pounds cruise at Mach 0.84, climbing to 45,000 feet final altitude, covering 2,080 nautical miles
- 1,000 pounds reserves for 20+ minutes Sea-Level Loiter or 150-200 nautical miles Divert
2,140 nautical miles
(F-16B Two-Seater has 12,800 pounds fuel for 1,880 nautical miles range)
General Dynamics Stated Range for F-16A: 2,100+ nautical miles
Now, I will list the JF-17's estimated calculations first and then discuss them:
---
JF-17 Block I/II Ferry Range (14,500 pounds Aircraft Empty Weight):
Internal Fuel (5,000 pounds usable) + 800 Liter Centerline Drop Tank + Two 1,100 Liter Drop Tanks
26,500 pounds Takeoff Weight
10,000 pounds [6,000 liters] usable fuel
- 400 pounds taxi & takeoff
- 700 pounds climbout covering @ 50+ nautical miles
- 8,100 pounds cruise covering 1,800+ nautical miles
- 800 pounds reserves for 20 minutes Sea Level Loiter or 200 nautical miles Divert
CAC/PAC Stated Range: 1,880 nautical miles
---
Notes:
1. Warmer than standard temperatures at cruising altitude may reduce ferry range slightly (1-5% for some portions of flight).
2. Afterburner (A/B) assisted takeoffs require additional fuel reducing ferry range by @ 100 nautical miles. In practice, Afterburners are likely to be used when carrying more than just a Centerline Drop Tank, in order to shorten takeoff distances.
3. Not being able to cruise at optimum altitudes/airspeeds for some portions of flight may reduce ferry range by 50-200 nautical miles.
4. Headwinds encountered during some portions of flight may reduce ferry range by 50-250 nautical miles.
5. Extra Stores such as Cargo Pods and Missiles will reduce ferry range by @ 100-150 nautical miles.
---
Units:
One Nautical Mile [nm.] = 6080 Feet [ft.] = 1.15 Statute Miles [mi.] = @ 1.85 Kilometers [km.]
One Pound [lb.] = @ 0.4535 Kilograms [kg.]; One Kilogram = 2.205 Pounds
1,000 Pound-Force [lbf.] Thrust = @ 4,450 Newtons = 4.45 Kilo-Newtons [kN.] Thrust
Kilograms are units of mass and the term Kilogram-Force [kgf.] is meaningless.
One US Gallon = 3.785 Liters = @ 6.84 pounds JP-8 fuel; One Imperial Gallon = 4.54 Liters; One Liter = @ 0.82 Kilogram JP-8
---
We see that the JF-17 is about 80% the weight of an F-16A, it has very similar trapezoidal wings, and the engine produces roughly 80% the thrust of the F-16A's original F-100-PW100 engine and is about as fuel-efficient as that engine (actually better when in afterburner).
The fuselage cross-section is also very compact and the DSIs are known for being efficient at speeds from Mach 0.4 to 1.6. It is practically impossible to calculate drag (at-lift, induced, trim, wave, or any other) without taking a scale model to the wind tunnel but we might estimate some of these from our experience later on.
Right now, we are most interested in the two aircrafts' subsonic cruise efficiency. The F-16 has a specific range in cruise of (2,080 nautical miles / 11,700 pounds fuel =) 0.178 nautical miles/pound. The JF-17 has a specific range of (1,830 nautical miles / 8,100 pounds fuel =) 0.226 nautical miles/pound.
Thus, we find that the JF-17 consumes roughly 80% of the fuel in subsonic cruise as the F-16. What this posits for us is that the JF-17 is probably as efficient in subsonic cruise as the class-leading F-16 was. We can thus safely assume that the aircraft (normalized to the F-16) is as efficient in producing lift and reducing drags during subsonic cruise.
Of course, this does not give us any idea of subsonic and supersonic maneuver-time drags. But those have more to do with turn rates, and fuel consumption will be predicated primarily by afterburner use. Similarly, non-optimal speed/cruising altitude consumption can be estimated with some certainty later on, given that the planform of both aircraft are similar and we have reasonably established that the JF-17 is not much draggier than an F-16.
On an aside, please note that the Blended-Wing-Body (BWB) planform of the F-16 produces 30-40% of its lift from its fuselage during high-AOA turning maneuvers. From NASA's BWB studies in the 1950s and experience of other aircraft, the JF-17's fuselage probably contributes only 20-30% lift under these conditions.
The JF-17's wings are, however, more than 80% the size of an F-16's (263 square feet vs. 300 square feet) and it has large Leading Edge Root Extensions (LERXs). These factors, as well as a good power-to-weight ratio, relaxed static stability, and digital pitch-axis Fly By Wire (FBW) should make it reasonably maneuverable in the Mach 0.6-0.9 dogfighting regime at 10,000-20,000 feet altitude.
Lastly, please note that the F-16A we used as a benchmark here had a fuel fraction of (14,000 pounds fuel / 33,000 pounds takeoff weight=) 0.425 and the JF-17 has a fuel fraction of (10,000/26,500 =) 0.375. The F-16C from our afore-mentioned analysis had a fuel fraction of (14,000/36,500 =) 0.385 and we had estimated its ferry range in this configuration at approximately 1,900 nautical miles.
So, if you can compensate for engine efficiency and drag issues, a fuel fraction gives you a good idea about a fighter aircraft's range. Fighters that carry all fuel and payload internally (or conformally) will have an advantage here. However, if the fighter with external non-conformal carriage is allowed to drop its tanks when empty, it can even come out slightly ahead.
As always, please feel free to point out all mistakes. I will be happy to correct them, Insha'Allah.
Allah keep everyone safe.
Following on from :
F-16 Ferry Range Analysis
https://defence.pk/threads/pakistan-f-16-discussions-2.15226/page-649#post-8906190
and
F-16 Combat Mission Radius Analysis
https://defence.pk/threads/pakistan-f-16-discussions-2.15226/page-649#post-8916212
I was going to post the analysis of the JF-17's ferry and combat ranges to the JF-17 Discussions thread, but that thread is infested with trolls and flamers.
If there are no objections, I would like to start by analyzing the ferry range of the JF-17 today, and we will attempt to see how it was designed to PAF requirements, after we are done with the combat range analysis later in the week, Insha'Allah.
To recap, please recall from the F-16 Ferry Range Analysis part:
"I have been working on an analysis of ferry and combat ranges for active fighter aircraft. The conclusion will seem to be that (except for a couple of outliers) these figures are mostly similar for most modern combat fighters/attack aircraft. Not surprising considering that, no matter from what country the planes originate, they are usually designed to broadly similar payload/performance/range requirements.
...
I started with the F-16 because it's charts are widely available and can be checked online. So, it will form a baseline for assumptions to be made when data are not fully available for other aircraft.
No classified information will be presented in the analysis and (for the sake of alarm-raisers) any country that might be interested in the figures will have more accurate data and much more (tactics and capabilities) already made available to them by the manufacturer. The F-16 has been demoed to just about everybody including India.
The figures have all been rounded after calculations to make them more readable (and the roundoffs adjusted, for the nitpickers, so that they add up and/or are consistent)."
Now on to the task at hand. There have been many conflicting statistics on the JF-17's combat ranges. Not surprising given that operational & environmental conditions, takeoff & reserves requirements, and the need to evade enemy defenses, all of these exclude the possibility of fixing a hard number to a mission radius figure. Please recall that for the F-16C examples we worked out, the combat radius ranged all the way between 65 and 670 nautical miles.
For most aircraft, the only hard constructor-claimed range estimate you can seriously consider is the ferry range. This is usually stated under very well-known standard conditions with the aircraft flying under optimum cruise conditions all the way from Point A to Point B, with a nearly standard landing reserve.
We have a very good figure of 1,880 nautical miles for the JF-17 with three external tanks that has been validated by its overseas deployments. After considering all the claimed estimates and data, I decided to form this as the basis of my JF-17 analysis. It gives us a baseline for the JF-17's subsonic-cruise fuel consumption that should serve us well later, Insha'Allah.
Recall for the F-16A's ferry range with three tanks, we calculated:
F-16A Block 15 Ferry Range (16,300 pounds Aircraft Empty Weight)
Internal Fuel + 300 Gallon Centerline + Two 370 Gallon Drop Tanks
33,000 pounds Takeoff Weight
14,000 pounds [7,800 liters] usable fuel
- 500 pounds taxi & takeoff
- 800 pounds climbout to 36,000 feet initial cruising altitude, covering 60 nautical miles
- 11,700 pounds cruise at Mach 0.84, climbing to 45,000 feet final altitude, covering 2,080 nautical miles
- 1,000 pounds reserves for 20+ minutes Sea-Level Loiter or 150-200 nautical miles Divert
2,140 nautical miles
(F-16B Two-Seater has 12,800 pounds fuel for 1,880 nautical miles range)
General Dynamics Stated Range for F-16A: 2,100+ nautical miles
Now, I will list the JF-17's estimated calculations first and then discuss them:
---
JF-17 Block I/II Ferry Range (14,500 pounds Aircraft Empty Weight):
Internal Fuel (5,000 pounds usable) + 800 Liter Centerline Drop Tank + Two 1,100 Liter Drop Tanks
26,500 pounds Takeoff Weight
10,000 pounds [6,000 liters] usable fuel
- 400 pounds taxi & takeoff
- 700 pounds climbout covering @ 50+ nautical miles
- 8,100 pounds cruise covering 1,800+ nautical miles
- 800 pounds reserves for 20 minutes Sea Level Loiter or 200 nautical miles Divert
CAC/PAC Stated Range: 1,880 nautical miles
---
Notes:
1. Warmer than standard temperatures at cruising altitude may reduce ferry range slightly (1-5% for some portions of flight).
2. Afterburner (A/B) assisted takeoffs require additional fuel reducing ferry range by @ 100 nautical miles. In practice, Afterburners are likely to be used when carrying more than just a Centerline Drop Tank, in order to shorten takeoff distances.
3. Not being able to cruise at optimum altitudes/airspeeds for some portions of flight may reduce ferry range by 50-200 nautical miles.
4. Headwinds encountered during some portions of flight may reduce ferry range by 50-250 nautical miles.
5. Extra Stores such as Cargo Pods and Missiles will reduce ferry range by @ 100-150 nautical miles.
---
Units:
One Nautical Mile [nm.] = 6080 Feet [ft.] = 1.15 Statute Miles [mi.] = @ 1.85 Kilometers [km.]
One Pound [lb.] = @ 0.4535 Kilograms [kg.]; One Kilogram = 2.205 Pounds
1,000 Pound-Force [lbf.] Thrust = @ 4,450 Newtons = 4.45 Kilo-Newtons [kN.] Thrust
Kilograms are units of mass and the term Kilogram-Force [kgf.] is meaningless.
One US Gallon = 3.785 Liters = @ 6.84 pounds JP-8 fuel; One Imperial Gallon = 4.54 Liters; One Liter = @ 0.82 Kilogram JP-8
---
We see that the JF-17 is about 80% the weight of an F-16A, it has very similar trapezoidal wings, and the engine produces roughly 80% the thrust of the F-16A's original F-100-PW100 engine and is about as fuel-efficient as that engine (actually better when in afterburner).
The fuselage cross-section is also very compact and the DSIs are known for being efficient at speeds from Mach 0.4 to 1.6. It is practically impossible to calculate drag (at-lift, induced, trim, wave, or any other) without taking a scale model to the wind tunnel but we might estimate some of these from our experience later on.
Right now, we are most interested in the two aircrafts' subsonic cruise efficiency. The F-16 has a specific range in cruise of (2,080 nautical miles / 11,700 pounds fuel =) 0.178 nautical miles/pound. The JF-17 has a specific range of (1,830 nautical miles / 8,100 pounds fuel =) 0.226 nautical miles/pound.
Thus, we find that the JF-17 consumes roughly 80% of the fuel in subsonic cruise as the F-16. What this posits for us is that the JF-17 is probably as efficient in subsonic cruise as the class-leading F-16 was. We can thus safely assume that the aircraft (normalized to the F-16) is as efficient in producing lift and reducing drags during subsonic cruise.
Of course, this does not give us any idea of subsonic and supersonic maneuver-time drags. But those have more to do with turn rates, and fuel consumption will be predicated primarily by afterburner use. Similarly, non-optimal speed/cruising altitude consumption can be estimated with some certainty later on, given that the planform of both aircraft are similar and we have reasonably established that the JF-17 is not much draggier than an F-16.
On an aside, please note that the Blended-Wing-Body (BWB) planform of the F-16 produces 30-40% of its lift from its fuselage during high-AOA turning maneuvers. From NASA's BWB studies in the 1950s and experience of other aircraft, the JF-17's fuselage probably contributes only 20-30% lift under these conditions.
The JF-17's wings are, however, more than 80% the size of an F-16's (263 square feet vs. 300 square feet) and it has large Leading Edge Root Extensions (LERXs). These factors, as well as a good power-to-weight ratio, relaxed static stability, and digital pitch-axis Fly By Wire (FBW) should make it reasonably maneuverable in the Mach 0.6-0.9 dogfighting regime at 10,000-20,000 feet altitude.
Lastly, please note that the F-16A we used as a benchmark here had a fuel fraction of (14,000 pounds fuel / 33,000 pounds takeoff weight=) 0.425 and the JF-17 has a fuel fraction of (10,000/26,500 =) 0.375. The F-16C from our afore-mentioned analysis had a fuel fraction of (14,000/36,500 =) 0.385 and we had estimated its ferry range in this configuration at approximately 1,900 nautical miles.
So, if you can compensate for engine efficiency and drag issues, a fuel fraction gives you a good idea about a fighter aircraft's range. Fighters that carry all fuel and payload internally (or conformally) will have an advantage here. However, if the fighter with external non-conformal carriage is allowed to drop its tanks when empty, it can even come out slightly ahead.
As always, please feel free to point out all mistakes. I will be happy to correct them, Insha'Allah.
Allah keep everyone safe.