I would have thought F-16 C had more range than A. Any thoughts on why the A can go further?
Any comparison available about how much is the CAP for JF-17 Block II and upcoming Block-III ?
Bismillah ir Rahman ar Raheem
Now, when estimating the combat radius for the JF-17, we need to keep in mind that the drag- and weight- induced fuel consumption penalties for the smaller, lighter JF-17 will be more for an equivalent payload when compared with our F-16 baseline.
Our calculations are somewhat simplified by observing that the payloads carried by the JF-17 are usually very simply aligned into the air-stream and with respect to each other. There are not many munitions carried concurrently (at one time). Interference drags (caused by airflow disturbance in-between stores and between pylons) seem to be well-controlled also.
However, the drag of stores compared to the clean aircraft (no external stores) or ferry-configured aircraft will be higher as a percentage of the clean (or ferry-configured) aircraft's drag. This is nothing new; this percentage effect of a store's drag (called its drag index) is obviously going to be smaller for the already larger, draggier airframes - the store's drag remains the same, its proportion to the different airframe's drags changes.
As an example, the drag index of a single 600 US gallon wing drop tank is 28 (% of the total clean-airframe drag) of an F-16C, but only 12 for the much larger F-15C (not sure with or without pylon drag), and just 2 for the very draggy A-10. The drag index of a store also increases in conjunction with what else is carried externally (due to the interference drag we mentioned earlier).
It can be safely assumed that the drag index of an equivalent store on the JF-17 is probably going to be more than 25% higher than for an F-16. How much it is exactly, is going to be open to much conjecture without resorting to an accurate JF-17 model and a wind tunnel.
For the F-16 (whose charts are available on-line) we can safely assume that our optimal range calculations were within a few percentage points of reality. However, for the JF-17, even if all assumptions are very carefully considered, our mission radius calculations will be fortunate to be within 10% of the actual figures.
Also, please keep in mind that a total stores drag index of 100 means that the aircraft is twice as draggy as when clean. However, it does not mean that it will consume twice as much fuel. At similar weights, the fuel consumption might only increase by 20% in cruise. Increasing weight without increasing drag generally has a somewhat proportional effect on fuel consumption.
Now, for the JF-17 we have one very important measure of combat radius, its CAP (Combat Air Patrol) endurance from the PAF. It is safe to assume that this measure was defined by the same metrics and assumptions used by General Dynamics (not necessarily the same as ours) for measuring the F-16A's CAP endurance.
Fortuitously, we found that the JF-17 in a very similar ferry configuration to the F-16 used about 80% of the fuel per nautical mile. So, without more ado, let us see if we can scale our F-16 charts to fit the JF-17 and come to a CAP endurance estimate close to the PAF's.
---
Mission Profile I - Combat Air Patrol [CAP] 200 nautical miles from base
JF-17 Block I/II (14,500 pounds Aircraft Empty Weight)
Internal Fuel + 800 Liter Centerline Drop Tank + Two 1,100 Liter Drop Tanks + Two SD-10A + Two PL-5EII
28,000 pounds Takeoff Weight [TOW]
10,000 pounds [6,000 liters] fuel
- 500 pounds taxi & takeoff
- 1,700 pounds climbout & cruise (total 200 nautical miles) to CAP area
- 4,700 pounds stay on station for one hour and fifty minutes
- 1,600 pounds reserves for 5 minutes dash and two minutes afterburner combat
- 700 pounds cruise up to 200 nautical miles back to base
- 800 pounds reserves for 20 minutes Sea Level Loiter or 200 nautical miles Divert
@ 1 Hour 50 Minutes at 200 nautical miles from base
PAF Stated Endurance for CAP mission: 1 Hour 45 Minutes
---
Notes:
1. Warmer than standard temperatures at cruising altitude may reduce range slightly (usually 1% to 2% , but up to 10% for some portions of flight).
2. Afterburner (A/B) assisted takeoffs require additional fuel, reducing combat radius by @ 50 nautical miles (or endurance by 15 minutes).
3. Not being able to cruise at optimum altitudes/airspeeds for some portions of flight may reduce endurance by 5-15 minutes.
4. Headwinds encountered during some portions of flight may reduce combat endurance by 5-10 minutes.
5. Every minute of afterburner use at medium-high altitude consumes as much fuel as 20 to 10 minutes of optimum cruise (or CAP endurance).
---
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
---
These figures were surprising to me. Using simpler metrics earlier, I had come to a CAP endurance for the JF-17 at 1 hour 35 minutes to 1 hour 40 minutes, 200 nautical miles from base. Remember, the heavy Block 50 F-16Cs that we calculated CAP endurance for came out at 1 hour 35 minutes under similar conditions (also surprising - expected it to be a bit higher; probably under-estimated the effect of the large engines and extra weight).
As always, all errors pointed out will be greatly appreciated. We will attempt to post our calculations for the other mission profiles later this week, Insha'Allah (hopefully simplified and with not as much exposition).
Allah keep everyone safe.
Check that out.
