The following was posted on the C-130 Hercules Headquarters Bulletin Board by Lucky Ekman who is Snow Aviation's Project Manager for the tip tank mod.

Thanks to all for your interest in Snow Aviation's (SAI's) tip tanks which we demonstrated on Earl Cherry's C-130A. Earl is authoritative on the program, and I was the Program Manager. I can add below some additional details which may be helpful:

1. The tip tank demo along with STOL Herk were briefed 18 Oct to the C-130 Technical Coordinating Group WorldWide Review, so eveything below is in the public domain.

2. Tip tanks are not yet FAA certificated or Militarily Qualified. C-130A installation was a one-off that we could not recommend for fielding on the relatively flimsy structure of the C-130A wing. Later C-130 wings are beefier, and could be candidates for installation, but for that, some users, like AFSOC or AMC, would have to fund a full flight test series that revalidated the envelope with the tip tanks. OSD and DARPA, program guidance for our current STOL Herk program to put 8-bladed props, aerodynamic control enhancing mods, and underslung 6000 lb static thrust turbofans on our C-130E testbed, are considering having us add the tip tanks to the end of the STOL Herk program to gather the E/H relevant data that would support an AFSOC or AMC decision fully to test the tip tanks for possible fielding on USAF Herks.

3. The hypothesis that 512 gal of tip tank fuel would provide the same range as 1360 gal of pylon tank fuel once the pylon tank drag is removed has yet to be proven. We did find on the C-130A that there was no apparent drag increase from the clean wing baseline to the tip tanked configuraiton, suggesting that the tip tanks rode free of any drag, and that their wing bending moment relief when filled improved overall wing efficiency. If we're told to put tips on the STOL Herk demonstrator, we'll get additional data to try to quantify the extent to which tips would provide the same range as the underslung pylon tanks. What is clear is that carrying less total fuel for nearly the same range will mean that more aircraft payload capacity would be freed for cargo rather than fuel, so the effect will be more payload range per pound of fuel burn, or an efficiency improvement for the Herk. We'll try to gather baseline cruise fuel consumption data for the all up STOL Herk configuration so as to be able to quantify the exact effects of tip tanks on cruise SFC if tips get added to STOL Herk.

4. During our original demo on the C-130A, we never landed the tip tanks and their load originally designed for the E/H with full tips because of the relatively lighter structure of the C-130A wing. If we're told to add tip tanks to the STOL Herk demo, we'll do a normal landing with full tips, but will likely find that assault landings should not be attempted with full tips. We'll plumb and manage the tip fuel so that it could be transferred inboard for assault landings and then returned if desired to the tips for wing bending moment relief effects after airborne from the assault strip.

Thanks for your interest in our tip tanks. Please watch the WR-ALC C-130 Technical Coordinating Group website for reports on our STOL Herk program over the next 12 months. Sherm Rankin has agreed to let us follow up on our 18 Oct briefing to the WWR by giving him updates for publication on the 130 TCG website.

Lucky Ekman
6 November 2005


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