Introduction
When I was young, I grew up next to a Boeing production plant. My family and I would tour this plant occasionally. This behind the scenes look at how Boeing worked inspired me. Ever since that time I have been interested in engineering and aviation.
A couple years ago I also found the remote control (RC) aviation hobby. This hobby was the perfect combination of my two greatest passions. In my time in the RC hobby, I stumbled upon the concepts of vertical takeoff and landing (VTOL). I was always intrigued by this concept because of its benefits,complexity, and the challenge it presented. But upon further investigation VTOL seemed too hard and time consuming for a young high schooler who liked trial and error better than research. Due to these fears, I never tried my hand at creating a VTOL of my own design. The Capstone class has allowed me to put the time into research and uncover the inner workings of VTOL. It has also inspired me to ask many questions. My research was focused on the following question.
Question
This question, however, inspired other smaller question that must be answered before a cohesive answer can be given. Some of these smaller questions that will be addressed are listed below.
In Depth Design Analysis
In general, vertical takeoff and landing systems use a mechanism to rotate the thrust of the engines to point directly downwards and thus propel the aircraft straight upwards. This is a common feature of any VTOL design, and this is a similar action to what a helicopter can do. This allows the aircraft to takeoff and land without requiring a long runway, but in some cases it also allows the craft to hover in air. These application will be discussed in the following paragraphs. This paragraph is focused on the how-to of do it yourself VTOL.
There is no one right way to design a VTOL plane. The main category of VTOL I will be focusing on is called fixed wing VTOL. This type of VTOL utilizes a “fixed wing” to generate the life that opposes gravity during standard flight. One example of a fixed wing aircraft is a Boeing 737, and an example of a not fixed wing aircraft is a helicopter. But, this category can be broken up further into more specific subdivisions. These subdivisions include: Tilt wing, tilt rotor, Jet lift, and fan life (“VTOL Problems Discussed”). Tilt wing designs rotate the wings and thus the connected engines to point the thrust vertically upwards. Tilt rotors are similar, however, in this case only the motor rotates. The jet and fan lift designs utilize the redirection of thrust from jets engines or electric ducted fan units (EDF).
All of these designs have different benefits and different draw backs. Tilt wing and rotor systems operate best at medium speeds due to the requirement of large propellers for takeoff (“VTOL Problems Discussed”). Jet and fan VTOL craft, however, will work best at high speeds and they offer good cruising efficiencies (“VTOL Problems Discussed”). However, Jet and fan designs can require complex mechanical systems to compensate for the lower propeller area. These pros and cons will determine which design is more ideal for the desired application, but neither is completely superior to the other.
Problems
Given the basic idea of how a VTOL plane works and is constructed, there are many problems associated with VTOL planes. The biggest problem associated with VTOL is the mechanical complexity. Full scale VTOL designs require large hardware and structural support to meet the requirements of a rotating motor, wing, or redirection of thrust. But, another question is safety. Many tilt wing and tilt rotor aircraft use large propellers that are too big to land when in the standard horizontal position. This presents a problem because then a VTOL plane of this kind would have so easy way of landing given an emergency such as engine failure where vertical flight is not possible. A pilot may be forced to land horizontally, in which case the propellers would be broken and the runway would be damaged. This is not an ideal solution, but may provide a final resort for pilots.
Another problem is thrust. VTOL planes require more thrust than the weight of the craft to properly achieve a vertical takeoff. The added weight of a reinforced frame must also be taken into consideration with this design. This can cause problems because engines and propellers may become larger than standard sized propellers thus requiring a larger rotation mechanism or larger landing gear. Problems like this cause a chain reaction that makes it harder to achieve the required thrust for a vertical takeoff.
A final problem with VTOL aircraft is the high speed corrections that must be made to ensure that the VTOL craft stays level. VTOL designs need to be able to change the thrust of each motor rapidly to correct for slight imbalances in the craft, wind, or other forces causing the plane to tilt to one side. However, conventional turboprop and piston engines cannot change speed and thrust very fast. This causes these gas engines to not be the ideal power system for VTOL aircraft.
One solution for this is the use of electric motors. Electric motors offer many benefits over their gas powered counterparts, such as simpler rotation systems, lighter weight, and others. But battery requirements are holding back these electric power plants. The Boeing 787 Dreamliner can carry 223,000 lbs of fuel. The same energy held in batteries would weigh 4.5 million lbs (“Masunaga, Samantha”). This limits the range of electric aircraft, but it does not make electric power unfeasible.
Benefits and Applications
Even though there are many problems associated with VTOL, there are also many benefits and applications unique to VTOL aircraft. One use of VTOL aircraft is for short takeoff and landing (STOL) purposes. STOL allows a VTOL aircraft to be overloaded with weight and still takeoff. Because the thrust is pointed partly forwards, the plane gains horizontal speed, which generates lift. This lift allows the plane to takeoff weighing more than the engines can life vertically.
One application is search and rescue. Search and rescue teams need fast aircraft that are capable of hovering. Helicopters offer a good solution to these needs, but VTOL planes can outperform helicopters in specific situations. VTOL planes are more efficient and can go farther than helicopters. In addition, due to the use of wings, they can also travel faster than helicopters. These two advantages should allow VTOL planes to be very useful for search and rescue, but it also requires very accurate hovering capabilities from the planes.
A further benefit of VTOL is the safety benefits. Current commercial planes use long runways, but VTOL planes do not require these runways. Commercial planes have crashed because of lack of runway. VTOL planes’ wouldn’t suffer from this problem and so they could be safer in that regard.
VTOL aircraft benefit from this ability to land vertically also in the freedom of this capability. Because these planes do not require a runway, they can land in many environments that standard fixed wing aircraft cannot. This gives them potential applications in consumer, military, and construction fields.
Current Contributors
Currently VTOL is being pursued by many large scale corporations. Boeing ‘s greased lightning is a good example of the type of research happening right now. The greased lighting is a tilt wing, electric, unmanned, VTOL plane that is being used to test this VTOL design and learn more about the tilt wing aerodynamics (“Anthony, Sebastian”). However, recently Uber and NASA have also team up to design a multirotor taxi service that may be implemented in Los Angeles in the future. This is a big step forward for VTOL planes, even though this project is not focused on VTOL planes itself. This is because, this project will show the practical uses of current battery technology (“Uber Announces Agreements”). In addition, a company called Lilium created an electric VTOL plane that they wish to implement in a similar manner as Uber. These networks of VTOL aircraft could vertically takeoff the top of a building and would provide faster travel over short distances where traffic can cause problems for ground vehicles.
Project and Conclusion
VTOL has many benefits that could help advance air travel, and transport. Due to these benefits currently VTOL can be implemented into society, but it would be restrained by battery technology. But, this downside can be avoided by only using these planes on short distance travel until battery technology is able to extend the range of these vehicles. I plan to create and test new VTOL configurations and designs to attempt and gather more data to as what works and what does not. This data will be recorded in qualitative observations, black box logging, and videos of each test flight. This data will be conducted for a couple different designs and will allow me to draw conclusions to as which design is best and when.
Works Cited
Anthony, Sebastian. “NASA's Electric Vertical-Takeoff Airplane Takes First Flight.” ExtremeTech, 20 Aug. 2014, www.extremetech.com/extreme/188338-nasas-electric-vertical-takeoff-airplane-takes-first-flight-aims-to-eventually-replace-the-helicopter.
“Design and Construction of a Novel Quad Tilt-Wing UAV.” Mechatronics, Pergamon, 8 May 2012, www.sciencedirect.com/science/article/pii/S095741581200044X.
Khurana, K C. “Aviation Management.” Google Books, Global India Publications, books.google.com/books?id=ESWo4Zl5g1IC&printsec=frontcover&dq=isbn%3A9380228392&hl=en&sa=X&ei=iZvzU4ugAdP3yQTf74KwCw&ved=0CB4Q6AEwAA#v=onepage&q=vtol&f=false.
Masunaga, Samantha. “No Flying Tesla? That's Because Electric Planes Are a Steeper Challenge than Electric Cars.” Los Angeles Times, Los Angeles Times, 9 Sept. 2016, www.latimes.com/business/la-fi-electric-aircraft-20160830-snap-story.html.
Mott, Nathaniel. “Six Questions About Uber's Plan for VTOL Aircraft.” Inverse, Inverse, 27 Oct. 2016, www.inverse.com/article/22858-questions-uber-elevate-flying-taxis.
“Technology.” Lilium, lilium.com/technology/.
“Uber Announces Agreements with NASA and Plans for Los Angeles.” The Electric VTOL News, 9 Nov. 2017, evtol.news/2017/11/08/uber-signs-agreement-with-nasa-on-traffic-management/.
“VTOL Problems Discussed.” Flight Global, 28 Sept. 1961, www.flightglobal.com/FlightPDFArchive/1961/1961%20-%201400.PDF+.