At what point does it become more feasible to purchase new aircraft types rather than upgrading them.

[helmutkohl]

For example (my numbers might be wrong)..

I've noticed some of the more advanced MiG-21 upgrades, such as the Lancer or the Bison costs around 5-10 million per aircraft
I believe Thailand's recent F-5 upgrades with Elbit also put it around the 10-20 million price per aircraft

while a used F-16 seems to hover around 20-40 million depending on variant.

at which point would it be more feasible to purchase a new cheap type (say FC-1, FA-50) o ra used 4th gen aircraft
over extensively upgrading 2nd or 3rd gen aircraft.?

 

[aim9xray]

Well, to name a few decision points:

1) When you've no remaining supply chain to support the 2/3 gen aircraft. (And you have cannibalized and attritted your fleet down to a minimally sustainable level).
or
2) When you've no remaining fatigue life in your 2/3 gen aircraft (or the OEM refuses to certify a life extension scheme - see Vulcan; or the OEM no longer exists as such to conduct a life extension effort and/or you've got no access to the OEM's original engineering data. Or, the OEM declines to do so because they have a shiny new airplane to sell you.)
or
3) When your 2/3 gen aircraft/systems are no longer a credible deterrent or competitor against [fill in the blank].

The French F-8E(FN) Crusader comes to mind for 1), 2) and 3).

The Swiss will hit 2) in about 2030 for their F/A-18C/D and Northrop Grumman is no longer making replacement modules for the center fuselages (CBR+).

 

[riggerrob]

Accounting practices can also make a huge difference.
Sometimes it is prohibitively expensive to import new airplanes or it requires an act of Parliament to buy any new airframes, but money can sometimes be found in the maintenance budget.

For example, circa 1985, a Canadian Armed Forces Sea King helicopter nosed-in while practicing water landings in a fresh-water lake. Rotors sagged chopping off the top of the windshield and tail cone. Since Sikorsky had long-since quit building Sea Kings, a windshield frame was bought from Augusta-Bell (Italy) and a tail cone from Westland (UK). Most of the other components in between needed to be over-hauled or replaced. Since all the immersed electronic, engines, rotor blades, gear boxes, etc. were already in the over-haul supply chain, they never really showed up in repair accounting.
IOW "consumables" were budgeted from a different accounting "shoebox."

In another example, Mexican imposed huge import duties on new airplanes, but off-shore maintenance incurred minimal tarriffs. Several civilian Cessna 185s were "rolled into balls of scrap metal" and shipped back to the USA for "overhaul." All the repairs cost more than a new airframe, but were not taxed when re-imported into Mexico.

 

[alertken]

hk: if only it was simple to A your Q...but it's not.

Shift from the vagaries of military to the more simple civil. Boeing 707s were financed initially for 20 years' utilisation, but that evolved to 30.
Singapore A/L is now sending Airbus 380s straight to dismantling at 10-ish years. There is no techno-fatigue-life explanation. The User judged: as parts the a/c is worth more than a second User might pay; my tax regime tells me to do this; there is no second-hand market; my business has evolved and I now prefer frequency to capacity.

So, read that across to military...and you can guess why SAAF is happy with DC-3s...because Mr Douglas would not recognise them. Engines,avionics...

The drivers for many Forces are: maintenance support - spares, data; Threat change: the Central American Mustangs and Thunderbolts finally had to go when some neighbours got jets; and labour-intensity of ownership. If a Nation moves from (cheap) conscription (getting a few useful months out of folk, but at not much cost) towards professionalism...then you need an avionics suite where a box tells you to change me, please.

 

[marauder2048]

Has anyone ever seen notional conversion or induction costs advertised for the JF-17 or the F/A-50?

For more advanced types, the fixed costs for converting to and inducting a new type can be
very large even in relative terms if the fleet sizes are small.

 

[riggerrob]

The US State Department just approved an $863. program to update avionics and missiles on the RCAF's CF-18As and Bs. They did not say which contractor will do the upgrades.

This follows a recent purchase of F-18A from Australia in lieu of a projected purchase of new F-18Ds from Boeing. The Prime Minister's excuse - for not buying new F-18D - was a tarriff war involving selling DHC-8 commuter planes to the USA. We suspect that the P.M. just wanted to spend the money somewhere else. Similar excuses have been raised about why Canada is not buying F-35s.

The official excuse also includes a promise that these upgrades are only to keep CF-18As in service until a new fighter arrives between 2025 and 2035.
Hah!
Given Canadian Defense procurement practices, 2035 is hopelessly optimisitic. I expect to see CF-18As still flying in 2045!
Hah!
Hah!

Comparatively young airliners (e.g. 8 years) get dismantled if they are from a short production run and the original factory is no longer making spare parts. AW&SW published an article on this salvage process last year.