From kls Sun Jan 17 02:37:15 1999 Path: bounce-back Newsgroups: sci.aeronautics.airliners Date: 17 Jan 99 02:37:15 From: arch6@mail.inlink.com (arch) Subject: Re: Drop tanks! References: Message-ID: Approved: kls@ohare.Chicago.COM Sender: kls@ohare.Chicago.COM Organization: McK&A In article , tedperez@hotmail.com wrote: > I keep reading about aircraft manufacturers struggling to extend > the range of their aircraft, and i was just wondering why not use > drop tanks? After all, if the plane can ferry an engine under > the wing (making the plane appear to have five!), then why not > drop tanks? First, fix your reply to reply once, you've posted five times. [Moderator's note: He only posted once. Perhaps your news server is having a problem. -- Karl] Drop tanks are a design, operations and maintenance nightmare. Design: Drag on a station pylon is very big (undesirable, minimizes payback). Conformal tanks reduce some drag but increase effective cross-section. All tanks require stressed attachment points and plumbing for: effective filling (residual fuel and partial fill hazards) effective draining (residual fuel and cg) effective transfer (drops-wings-(tail)-main bags, what order?) emergency dump (time, control and cg) Fire (detect, suppress, jettison?) Fire (extra fuel, skin thickness, vulnerability (also to ground vehicles)) Non-tank aircraft have over-designed landing gear and other "extra" weight. Operations: Now which aircraft have that configuration? How to shuttle aircraft through dispatches to the one or two routes that really need this gas. How to get tanks up/down loaded effeciently when not needed. Pilot training (normal and emergency) Maintenance: relays, wires, pressurization storage, shipping, prepositioning and relocation of tanks people quals to up/download (currency) corrosion control