Monday, October 10, 2011

The Paperless Cockpit: Low Carbon Flight?

Given that unnecessary weight is the bane of practical aviation, will the ditching of heavy and bulky paper-based flight manuals in favor of much lighter digital PDA based devices result in a more eco-friendly flights by lowering fuel consumption?

By: Ringo Bones

A news story was aired on the BBC back in July 6, 2011 on a planned phase-out of bulky and heavy paper based pilot’s flight manuals in favor of much lighter “digital” flight manuals apps stored on personal digital assistant like devices – i.e. i-Pads – in order to lower fuel consumption during flights. But will this work? After all, being dependent on i-Pad and other supposedly lighter-than-paper tablet type computers could introduce its own host of problems in a contemporary commercial airline cockpit.

Ever since the very early days of aviation, weight reduction has always been part and parcel that makes powered long-duration manned flight possible. Early aircraft engineers had been heard of talking – albeit apocryphally – of selling their grandmothers into slavery just to lower a few pounds of airframe deadweight without sacrificing airworthiness. Nowadays, aerospace engineers aim for deadweight reduction in order to lower a typical commercial airline’s carbon footprint in a typical 18-hour long haul flight.

Back to the potential hosts problems that supposedly lighter-than-paper i-Pads and other tablet computers could introduce in a contemporary cockpit. To anyone who’s been a “frequent-flyer” since the 1980s, its been already standard operating procedure that the flight and cabin crew in a typical commercial airline flight had always been prohibiting us from using our Walkmans, mobile phones and other portable consumer electronic gadgets during “critical” portions of the flight. Citing reasons of electronic / electromagnetic interference on the vital cockpit avionics and the plane’s flight control systems. Could the pilot, co-pilot and flight engineer’s use of a tablet computer / i-Pad instead of a non-electronic paper-based flight manual generate electronic interference that could wreak havoc on the vital cockpit avionics during critical portions of the flight?

And another thing, making sure that your “digital” tablet computer / i-Pad-based flight manuals have enough juice or battery power for the whole duration of a typical long-haul 18-hour flight is a Sisyphean task in itself. Charging your “digital” flight manuals on the same power source that powers the plane’s vital avionics is a sure recipe for unwanted electronic / electromagnetic interference; Electromagnetic compatibility review of digital flight manuals and avionics, anyone?

Friday, June 10, 2011

Battery Powered Propeller Airplanes: The Future of Aviation?

Long deemed to be an aviation engineering impossibility due to the low power-to-weight ratio of existing battery technology, are the newfangled airworthy battery powered propeller planes represent the future of aviation?

By: Ringo Bones

With the advent of battery technology of the last few years that now have almost similar power-to-weight ratio of gasoline powered piston engines, battery powered planes had made their mark for a few years now – in the remotely-controlled scale-model world at least. But are battery-powered propeller planes capable of carrying a pilot and significant payload represents the cleaner and greener future of aviation?
The Elektra One, designed by aviation engineer Calin Gologan is probably the first ever battery-powered propeller driven aircraft capable of carrying its own pilot that had been successfully flown and landed safely. Elektra One uses advanced lightweight rechargeable lithium polymer batteries – i.e. lithium iron phosphate batteries - that can make the plane fly 500miles non-stop on a single-charge. Though the design represent one step in making general aviation more climate friendly, making and designing one capable of flying with hundreds of passengers and tens of tons of payloads and capable of flying halfway around the world on a single-charge is still probably decades away.

Despite its unassumingly conventional design, the Elektra One is one aviation engineering tour-de-force. Its wings are made of high-strength composites having only a total weight of 30-kilograms but are designed to bear loads of up to 900-kilograms during dramatic maneuvers. The Elektra One’s electric motor – the main thing that makes it fly – weighs in at just 4.56-kilograms but is capable of generating 4-kilowatts or around 5-horsepower that drives a highly-efficient propeller design – capable of converting over 85% of its rotational energy into forward thrust - to send it into flight.

And fly it does using current rechargeable lithium iron phosphate batteries that still have less power-to-weight ratio than conventional petrol-fueled aircraft piston engines. But if rechargeable battery technology advances to the point where their power-to-weight ratio equals that or exceed petrol-fueled piston engines, then battery-powered propeller airplanes could truly represent the more environmentally-friendly future of aviation; unless of course another clever aviation engineer could figure out on how to make battery-powered jet engines.

Monday, May 16, 2011

UK’s Retirement of the Harrier Jump Jet: End of an Era?

Even though the 20th Century’s best “jump-jet” or VTOL was inevitably retired, does the decision mark an end of an era in vertical take-off aircraft technology?

By: Ringo Bones

The British Royal Air Force’s decision to retire the Harrier Jump Jet back in December 14, 2010 was probably seen as an end of an era to anyone who knew full well the capabilities of the 20th Century’s finest vertical / short take-off and landing capable jet fighter. And anyone with the good fortune of flying the Harrier Jump jet side-by-side with its Soviet-era counterpart – the YAK-36/38 better known to the West and NATO as FORGER – will attest that the Harrier is magnitudes better. The Harrier is now slated to be replaced by the 60-million US dollar STOVL variant of the F-35 Lightning JSF deemed by maker Lockheed Martin as the logical replacement for the F-16 Fighting Falcon. As the most widely exported wonder of British aerospace engineering, will retirement of the Harrier Jump Jet prove rather premature?

As one of the icons of the Cold-War era Western/NATO bulwark against the Soviet threat, the Harrier Jump Jet first started life as the Hawker P-1127 resulting from the late 1950s design of the British Hawker Siddeley Aircraft Corporation. Although there were plans for a supersonic capable version of the Harrier, this dream was inevitably scrapped by the realities of the fiscal austerity of late 1960s Britain.

The Rolls Royce Pegasus jet engine used in the Harrier Jump Jet is probably the only one of its kind that uses cascade-vane-nozzle technology – analog of the deflected-slipstream turbojet engine. This type of jet engine is basically a turbojet engine – or in the case of the Rolls Royce Pegasus jet engine a high-bypass turbofan jet engine specially designed with a special nozzle that has been fitted so that the propelling jet can be deflected vertically to permit vertical take-off and hovering, although the Harrier only carries enough cooling water to allow it to hover in a virtual standstill for only 90 seconds. The special nozzle is provided with adjustable vanes. Control in hovering flight is obtained with auxiliary jet reaction nozzles, and control in high-speed flight is obtained by conventional fixed-wing control surfaces.

Since entering service with the British Royal Air Force (RAF) and the Fleet Air Arm in 1969, the US Department of Defense was very impressed by the Harrier Jump Jet’s performance that it eventually bought “several” for service in the US Marines back in 1971. Despite of its vertical and short take-off capability, the Harrier Jump Jet can never go supersonic – its top speed is only a little over 700-mph. And it is a rather “thirsty bird” with a combat radius of only 300 to 700 miles. Nonetheless, the Harrier Jump Jet prove its worth during the Falklands War of 1982 by being able to shootadown supersonic-capable French built Super Etendards (comparable in performance to the McDonnell-Douglas A-4 Skyhawk) by piloting skill alone.

And by the mid 1980s, The British Hawker Siddeley Aircraft Corporation eventually allowed US plane-maker McDonnell-Douglas to manufacture its own version of the Harrier – the AV-8B with advanced composite materials used in fabricating its wings that eventually allowed the American version of the Harrier to carry more fuel and weapons than its British counterpart.

Even though the Harrier Jump Jet has proved its worth for much of the 20th Century, it is still plagued by two main problems that most Air Forces of the world are reluctant to buy it. The first one is the hot-gas ingestion problem where the Rolls Royce Pegasus engines “accidentally” ingests the hot gas from its exhaust leading to temporary compressor stall that makes the Harrier drop like a rock when taking off vertically and its range restrictions because the rolls Royce Pegasus jet engine is rather thirsty. The STOVL-capable version of the F-35 Lightning solves the hot-gas ingestion problem by using a dedicated lifting fan with a gear system that allows it to be coupled to the main jet engine. And since the F-35 is largely made of lightweight composites, it resulted in increased fuel efficiency. The added bonus of the F-35’s lightweight design is supercruise – i.e. it can go supersonic without using afterburners – the afterburners are only necessary when the F-35 wants to go faster than Mach 1.5; and there’s the added bonus of stealth capability. Sadly, the F-35 still has to prove itself in combat if it is really a worthy successor to the Harrier Jump Jet.