Urban Air Mobility

It is further away than most people will tell you. 

Everyone sees the electric quad-copters, like DJI and such, and wishes they could ride on one. It seems so simple, just scale it up, and it can carry you, and a friend. Easy enough to fly, it will be fantastic, they go fast, no congestion in the sky, life is good. Lets do it!

Wow, there is a lotta money being spent on these vehicles, and not just from dreamers and hobbyists, but real live aerospace companies. Bell, Airbus and Boeing are all looking at the space, and at least throwing out drawings of stuff that might work. To be honest, you'd be silly to not be looking at this space, just in case.

What few people are saying, though, these little multi-copters that do vertical take-off and landing are not going to be main stream. If you can't afford to fly around in a helicopter today, you will not be able to fly in one of the passenger carrying multi-copters either. The cost will be similar when all is said and done, to flying in a modern helicopter.

Right now the batteries are the limiting factor. Even with a DJI or other "drone" type multi-copter it takes at least twice as long to charge the battery as the flight was. A 15 minute flight will take about 30-45 minutes to charge the battery for the next 15 minute flight. If you are Uber or some other air taxi service, this will kill the economic model right away. Every vehicle will spend over 2/3 of it's time charging between flights. Swapping battery packs may be an option, since the operator can have multiple packs charging at each station, but that will preclude landing in your neighborhood.

The multi-copters are noisy! People complain about jet noise around airports, so they don't live near any. Imagine you neighbor flying to work at 5:30AM everyday in one of these multi-copters. You will be up at 5:30AM yourself, and might as well go to work, you are up anyway. Having dozens of these flying over a venue you are at will certainly be annoying, plus think of the congestion that may occur for concerts and sporting events. Yup, it will be like the roads, with vehicles flying in to pick up passengers, blocking the vehicles with passengers trying to leave. With 3 or 4 pads near a arena will certainly be a limitation.

There is talk about putting pads on top of buildings, or at least high up. Winds are usually stronger higher up. Near the ground you might only have a 10kt wind, but up 20 stories (200ft) the winds may be 30-40kts. There will be turbulence for sure, but imagine the up and down drafts around buildings, and each landing and takeoff will be quite treacherous. Bad weather will be a whole other challenge, with heavy snow or ice storms, these vehicles won't be flying at all.

The multi-copters have multiple single points of failure. If a single motor fails on a quad-copter, the vehicle is coming down, the other three motors will not keep the craft flying. A hex or octa-copter will survive a single engine failure, but will probably not be able to complete the mission. Motors are electro-mechanical devices, they fail in different ways (bad bearings, broken wires, etc). Electronics fail, sensors fail, batteries fail. There is only so much redundancy that can be added to the vehicle to make it safe enough.

(Helicopters have many single points of failure as well, but there are usually ways to at least get the aircraft on the ground safely when any of them fail. An example is fuel exhaustion, when the motor(s) quit, the rotors can store energy. The pilot can pitch the craft down, such that the rotor is collecting energy from the movement through the air, that just before touching down, the aircraft can use that energy to slow the craft down and land soft enough-autorotation).

The propellers on the multi-copters are typically fixed pitch light weight affairs. Being fixed pitch means they are optimized for one realm of flight, typically for creating lift (forward motion, is more lift in the rear propellers, than the front ones). Should an engine fail, they have no mass to store energy, and will probably spin the wrong way in descent to be used for autorotation. Being light weight, they can be damaged easily by foreign objects, including birds, rocks, hail, trees, and people.

Commercial certification

Five years is very optimistic certification timelines people are pushing today for these urban air vehicles. If people where flying in these vehicles everyday, even experimentally, I could see maybe something could get pushed through in 5 years. As things are, maybe there is a Chinese company that is occasionally flying with people semi-regularly.

The FAA, EASA and the other regulating bodies will not let one of these vehicles get certified until it has proven capable through rigorous testing. That includes off normal operations, high winds, poor weather, and broken systems. It will take years of testing to get one of these vehicles certified to carry paying passengers.

Plan B

As a pilot you are always taught to look ahead, and consider your options. If an engine fails, where will I go, if a bird crashed through the windshield what will I do. If another aircraft is near me how do I avoid it, etc. The multi-copter pilot or automation will need to consider all of these things as well.

The vertical takeoff/vertical landing craft will need a plan B for the vertical part. While the vehicle is between 20 and 75 feet off the ground, no parachute system will save the occupants. If the vehicle has a failure, and it is coming straight down, the people in the vehicle will get hurt. I think even 75ft is optimistic, and more likely 200 feet or more will be needed to operate a parachute to save the occupants from injury. Parachute fail occasionally, that is why skydivers carry 2, and a spare chute won't save a crashing vehicle below 200ft.

In horizontal flight, if a propeller is damaged or an engine is down on power, the vehicle will need to land soon. Is there a safe place to put down over an urban area? The planning needs to be done before the flight, or for sure before the event occurs. Weather changes sometimes quickly, can the vehicle handle the unforcast weather properly? The hybrid winged vehicles are better in some respects. They can usually glide in an engine failure situation, but is there a suitable place to land near where this happens?


We need to let the smart people look at this carefully, so that we don't hurt folks.

The A4A won't give up

I sorta promised, I would go on about my last post. I guess I didn't think it would take a month and a half. I thought either the AIRR bill would get jammed through and there would be no stopping it, or it would go away. It almost went away, it was put on a shelf.

Representative Shuster has left a hole in the budget for a private ATC. Of course Mr Shuster is a little too friendly with the whole A4A crowd. He ought to recuse himself from this discussion. Follow the money they say, well Mr Shuster gets quite a bit of money from the A4A. Draw your own conclusions about weather this gentleman is representing his constituents or not.

So there is an argument, as there always is when congress wants to change the FAA, we are still using "WWII technology called RADAR". Oh my, that antiquated RADAR technology is going to make the aircraft fall out of the sky. Modernization isn't happening as fast a someone wants it to. Satellite based separation is the future and we need it now.

The sad thing is, the FAA's ATC system supports satellite based navigation. The ERAM program added it long ago. ADS-B was part of CARTS that was replaced by STARS/TAMR which had ADS-B 15 years ago. The fact is, the airlines are whining that it will cost them too much to equip older aircraft with ADS-B by 2020. The US Air Force is also complaining that they don't have the budget to make the 2020 ADS-B deadline. The trouble isn't the FAA, the trouble is the users can modernize quick enough.

I guess it makes sense. If they add another bureaucracy to keep the process inefficient, then there will be someone else to blame when they don't make the deadline. The A4A and the airlines seem to be arguing the private ATC corporation will be better, faster and cheaper. NASA learned that lesson a long time ago, better, faster cheaper can't happen. In this case, Faster will be hung up in committees and interfaces. Better will be hung up with new management wanting to change and current employees explaining why the new way won't work. Cheaper, well, government right.

The Shuster/A4A bill will create this fancy corporation. There will be a board to make the critical decisions. Critical decisions will be things like what products should be funded. Since the board will be mostly airline appointments, the choices will generally benefit the airlines more than anyone else. Imaging a 9/11 type situation, where all the flights are ground stopped. Who will pay the corporation for the week the aircraft didn't fly? It'll take a government bailout probably, or the corporation will veto national security, and require the airlines fly their normal schedule.

The Senate FAA Reauthorization Act of 2016 (S. 2658) is welcomed by many of the aviation groups. I think they will take anything but the AIRR act. There are plenty of things wrong with this bill as well. It may go too far regulating airline fees and seat sizes and a few other things the airlines don't like. Amendments and markup can fix those things. A couple things that are bad in the bill is related to model aircraft, the bill requires training for operators, and safety standards for model aircraft that some argue would be difficult for manufacturers to meet. 

If someone has a rational argument as to how this private ATC system will work, send the comments here. I haven't seen any evidence that this is something other than a power grab by the airlines.

Private ATC

I know it has been a while since I posted something, but there is trouble, and it is related to flying. This will be a political post, if you don't like it, I understand. You won't have to read it. It seems this subject comes up every few years, but common sense prevails, and the private ATC and user fee rhetoric goes away.

Flying aircraft costs money. You have to pay for the aircraft, and all the wear on it, the fuel and other consumables. Then there is building airports, hangars and other real-estate items. Once you are in the air, there is air traffic control (there is air traffic control at some airports, but that is a minority). There are regulators, inspectors, people who change light bulbs and other maintainers of things.

Some how all the stuff has to be paid for. Today, most of the revenue to run the people, regulations and real-estate related expenses is covered by fuel taxes. There are other taxes of course, real-estate and sales and use tax that cover local expenses as opposed to the fuel taxes that take care of the federal expenses. The system today is running pretty good, when congress doesn't raid the aviation funds to pay for other items (I know they usually leave an IOU, but not always).

The airlines and congress are trying to change all this. Well, or make it more complicated. There is a bill introduced by Rep. Bill Schuster (from Pa.) called Aviation Innovation, Reform, and Reauthorization (AIRR) Act. It has several parts, including reauthorizing the FAA, adding private rooms for nursing mothers and requiring baggage fee refunds for bags delayed over 24 hours. The bill also wants to regulate drones (UAV's really), and outlaw voice calls on flights. The biggest thing the bill wants to change is to take air traffic operations (ATO) out of the FAA's hands and put it into another groups domain.

This new ATC (ATO) organization would be a not for profit corporation who's sole purpose would be to handle the air traffic operations. All the current air traffic controllers would be part of this new corporation. Managers, janitors, planners, office assistants, controllers, supervisors all would be part of this corporation. All the equipment, and buildings would be a part of this new organization. The hope is, that the users would pay for this service.

The argument is that "modernization" isn't happening fast enough. Moving all the air traffic operations out of the FAA, they argue, will streamline the modernization. The specifics of this new modernization are not covered or explained. There is vague future kind of hope. The sponsors of the bill offer some of the current "NextGen" initiatives haven't happened quickly enough.

The sponsors of the bill say the FAA will focus on what it does best providing safety. No question, the FAA does provide guidance allowing the US to be one of the safest countries to fly in. Between testing, regulations and regular information bulletins (SAIB) the pilots, owners and operators are well informed (if they want to be).

The sponsors of the bill also want to convince us that the USA is the only large industrialize country that doesn't have a separate air traffic organization. The fact is, the US airspace and operations are far different than any other country. The USA allows much more freedom for most pilots. Pilots many times don't have to talk to anyone in air traffic control for their whole flight. A small airport will typically not have a control tower. Pilots coordinate their own separation at these airports using the radio and a "party line" frequency (CTAF). Once in the air, most of the US airspace does not require communicating with air traffic control. Once in the area of an airport with a control tower, then communications must be established.

Canada has more open airspace than the US. Canada has less populated areas, so it is common to not have need to talk to airtraffic control for hours. Nav Canada is the not for profit corporation Canada set up to run their ATO. They have a simple book explaining their fees. For a Cessna 182 based out of Moose Jaw Municipal Airport (CJS4) that may fly in the area, never landing at Ottawa, Edmonton or Alberta airports the fee may be as little as $68 per year. If the same aircraft were a Falcon 50, the fees would be significantly higher starting with a $227 base fee + miles and services used.

While Nav Canada seems to be a model to follow, in less than 15 years from it's founding (Nov 1, 1996-Jan 12, 2009) the corporation became illiquid. The hope is that the note that were issued to make the corporation solvent will mature in 2017, and will be fully paid back. The funding for the interest on those note came from the users of the service. So while the corporation is non-profit, it still needs to break even. Fees the users pay must match the needs of the corporation. Canada also charges a tax on Av Gas, but that goes to the federal government, not to Nav Canada.

This separate corporation will need to build infrastructure. There are buildings that need repair, computers that need upgrades, RADARs that need maintenance, etc. The fees need to cover current costs, as well as plans for the future. If an airport needs to add new equipment to a control tower, there must be money available to cover that. The fees need to be based on projected operations, for the following year. (it is tough to collect proactive fee increases). The modernization will cost money, that the non-profit company has to spend.

Many pilots are challenged to find the money needed to go flying as it is. While most people see all the corporate jets on the ramp at their local airport, in the hangars and tie downs are all the affordable aircraft. Owners of these aircraft skip lunches, drive crummy cars, and do what they need to to be able go fly once a week in their plane. When the local people can't fly, the fee model gets skewed, and the big guys pay more fees. The airlines don't pay these fees out of the kindness of their heart, they pay them with higher ticket prices.

There are also two edges to this sword. If traffic increases in an area, there may not be staff to cover all the services needed. The budget was set, and it may not allow additional staffing for temporary situations. Likewise, pilots may avoid asking for services when in an area if they believe they can get by without it due to costs, even though the weather is deteriorating. Either way safety is not at the top of the priority list.

The agility will be compromised by having a separate ATO corporation from the safety group. If the ATO wants to make a change that may affect safety, there will need to be meetings and specific plans nailed down and approved by committees of both corporations. Committees are not always the most functional groups, so that will add time and complexity.

Additional bureaucracies will need to be added. There will need to be safety audits of the ATO corporation by the FAA. This functionality will expand as needed until both groups are unable to operate well. There will also be fee collectors, and auditors for that functionality.

While it may seem congress is doing this on their own, they aren't. The Airlines For America (A4A) is the biggest proponent of this action. The A4A is the big lobbying group for the airlines in the US. Even within the ranks of the organization, not everyone agrees with privatizing ATC. Delta airlines quit the A4A because of this action.

Over all, the plan for a private ATC system will end up costing the users (anyone who flies, passenger, pilot or cargo) more money. It may seem like a simple answer, but in the end, the corporation will grow, the FAA won't shrink, congress won't cut fuel taxes and the new corporation will collect ever increasing fees.

Show me where I am wrong!

GPWS, TAWS and HTAWS

Controlled Flight Into Terrain (CFIT), and other troubles are common for all aircraft. Obstacles are out there, the trick is avoiding them. The FAA has come up with various equipment that can help minimize the surprises obstacles may offer.

beware...lest the ground rise up and smite thee

It wouldn't be an FAA requirement if there wasn't a technical standard order (TSO) to go with it. TSO-C151B covers terrain awarness and warning systems (TAWS). Ground Proximity Warning Systems (GPWS) are covered in this as well. Helicopter Terrain Awareness and Warning Systems (HTAWS) are covered in their own TSO-C194. For the most part, all the systems work similarly, the main difference is the performance of the aircraft.

Most TAWS systems work by knowing where the aircraft is and checking a terrain database to know if there are obstacles in the path of the aircraft. Knowing the trends (is the aircraft climbing or turning, etc) will allow a computer to know how much of the database needs checking. A current altitude source is needed. Sometimes this could be the barometric altitude, other time it may be a radar altitude.

There are various databases of terrain available. Either from the FAA or other sources. The FAA makes available the current database, and a daily update that will include construction cranes, and other changes to obstacles.  The daily update file (DDOF) is available as the whole current database, and also just the changes.

The TAWS must be looking along the path of flight to function. The distance ahead is critical, especially at cruise altitude and speed. While most 121 aircraft are capable of clearing all but the highest mountains in the world, the assigned flight level or performance with fuel and passengers may not allow the current flight to climb over all the enroute terrain.

During approach to landing, and departure, there can be many more obstacles. Buildings, trees, construction cranes, and radio towers can be near airports. The TAWS must also consider these obstacles locations and provide safe clearance to avoid them.

Generally the TAWS should provide warnings if the aircraft is or will be between 100ft and 400ft of an obstacle during departure, and less than 1000ft during enroute portion of flight.

Within the TAWS there are various classes of capabilities provided by the systems. The classes are broken down as:

• Class A: Alerting based on; excessive rates of descent, excessive closure rate to terrain, negative climb rate after take-off, flight into terrain when not in landing configuration and excessive downward deviation on ILS approach. It will have voice alerting and sweep tones. It must also have a terrain display. 
• Class B: Similar alerts, but with wider tolerances as the class A alerts. Class B assumes no Radar Altimeter, and the base threshold of the runway altitude. There must be an altitude call out for 500ft and other alerts, but class B TAWS does not require a display. 

TAWS systems are required on some aircraft. All part 121 turbine aircraft must have a class A terrain awareness and warning system (121.354). All part 135 turbine aircraft that seat 6-9 passengers must have a class B TAWS (135.154). Even part 91 turbine aircraft that seat more than 6 seats must have a class B TAWS. More details are in AC25-23. 

While TAWS have not eliminated all CFIT accidents, there are many situations where the systems have proven to save lives. 

The FAA is Still Trying To Save Face

ADS-B again...

The FAA is offering relief from the 2020 deadline, only this time is not just Part 121 air carriers but all aircraft, even GA!

It is all pretty qualified, you still need to try to meet the 2020 deadline. The only relief is really in the position source and it's level of service. For ADS-B the FAA wants C-145/146 WAAS type level of accuracy. That is a good thing, since the more accurate your ADS-B location is the fewer alerts others may get.

The is this old joke:

Tower: "Alpha Charlie, climb to 4000 ft for noise abatement" 
Pilot: "How can I possibly be creating excess noise at 2000 ft?" 
Tower: "At 4000 ft you will miss the twin coming at you at 2000 ft, and that is bound to avoid one hell of a racket".

And with poor location indication, something like this could happen.

Will the FAA be official about any of this anytime soon? Probably not. They most likely don't want you to know anything about it, and would rather have all aircraft fully compliant on 2020. But for folks with older GPS receivers or pre-2013 ADS-B capable installs it will be nice to not have to rush for a full panel upgrade.

It only relief. It isn't full abandonment of the rules. The full rules will still go into effect 2025 or so they say.

I know the reluctant airlines are making an effort to upgrade. I would agree they should be reluctant. The FAA has encouraged them to move forward in RNP, and other NextGen projects only to loose support after the aircraft were upgraded.

Maybe the FAA will play ball this time.

Load The Bags In The Back

Weight and balance in aircraft is very important. On occasion, you'll see or hear about an aircraft that crashes because of weight and balance issues. Usually the weight is placed too far aft, and suddenly the plane is uncontrollable. Normally it will happen in GA aircraft, but occasionally in transport types there will be too much weight too far aft.

The image above was a 747 where the cargo broke loose after takeoff (or on rotation), and as the aircraft pitched nose up, the cargo slid to the rear. The elevator authority was exceeded, and the pilot was unable to get the nose down before impacting terrain. As the cargo slid aft, the aircraft pitched further up, causing anything loose to go further aft. Eventually the engines couldn't lift the aircraft, so it began falling. 

GA aircraft don't have to have restraints change. So aircraft are tail heavy to start with, and loading things in the rear will make things even worse. Fortunately most aircraft are designed to allow seats to be utilized and some cargo in the rear, and will remain in the loading envelope. 

Most aircraft have a center of gravity (CG) envelope similar to:

Where as the aircraft gets heavier, some weight may not be allowed too far forward or aft (the angles at the top of the graph). The seats are usually in the middle of the graph and the front and rear cargo holds are the front and rear limits of the chart. 

If the aircraft is loaded outside of the envelope, the aircraft will have control issues. Too far aft, and the elevator may not be able to keep the nose down. Too far forward, and the elevator may not be able to lift the nose off the runway. 

There are two points that need to be close to fly stable. The center of lift (where all the lift vectors converge) and the center of gravity (where all the weight vectors converge). If the CG and CoL are exactly at the same point, the aircraft may fly fine. If there is an engine out, with the CoL and CG together, it may be more difficult to glide. Most aircraft fly with the CG ahead of the CoL as a safety precaution. With the CG ahead of the CoL, the nose will drop to help maintain airspeed, and the aircraft will glide nicely with an engine out. 

Moving the CG too far forward will cause extra fuel burn. The elevator will have to push down more to keep the nose up. This pushing down is actually adding to the weight the wings are needing to carry, so the aircraft will have to fly at a higher angle of attack, meaning the aircraft will be extra draggy. 

Aircraft are designed with a specific known airfoil. The airfoil has certain characteristics, and the designer will choose one the meets the criteria of the aircraft. The aircraft will have an optimum load point, which we call the CG. The CG in large transport aircraft the optimum point is measured in a mean aerodynamic chord, or percentage of the wing to operate at. There is a range that is safe, a range that is good and a sweet spot where the is minimum trim drag, or up elevator. 

Most transport aircraft have a sweet spot with a high percentage of the bags in the rear of the aircraft. This will minimize fuel burn, and allow quicker loading of the aircraft. 

FYI  

Electrical System Basics

This post is about electrical system basics, what powers what and why. Not all aircraft have electrical systems, but the ones that do, it is all the same.

In a car, there is a battery, mostly used to start the motor. When the motor runs, there is some excess horsepower used to drive an alternator that is used to recharge the battery and run all the electrical systems in the car. If it didn't have enough power to run everything and recharge the battery, the battery would always be dead.

In an aircraft there are batteries that will start the aircraft. Your normal GA aircraft will probably have a single battery that will be enough to start the motor. Some will be 12V and others 24V. The voltage doesn't matter the concept is the same. The battery starts the motor, and the alternator powers all the other systems while recharging the battery. Light jets are similar, but some will have a starter/generator. The starter once the engine is going will become the generator, to power the electrical systems.

In larger jets, like the 737, there will be a battery, but it will be used to start the APU. The APU is a small engine that turns a generator. The APU will generate enough electricity to start the bigger jet engines. The jet engines have starter/generators on them, that will be used to power the whole aircraft and recharge the batteries.

Many times, jets will use a ground power unit (GPU). This is a cart with an engine and generator or interface to mains power that will be used to power the aircraft while on the ground, and can be used to start the aircraft.

Once the aircraft is powered, there are many systems. These systems can include avionics, entertainment, lighting, etc. Each of these systems will have one or more circuits. Each circuit will be protected with a fuse or circuit breaker (or an electronic equivalent). The circuit protection device is there to prevent fires. The size of the circuit protector is related to the size of the wire going to the circuit. In an aircraft smaller wires mean less weight, so using the right size is critical.

As current flows through a wire, there is resistance. Copper has very low resistance, but not zero. That resistance to the current flowing translates into heat. If the wire cannot dissipate the heat generated, it will transfer the heat to the insulation, potentially melting that. If the insulation melts, and maybe melts the wire next to it, or as the wire passes through a bulkhead and can conduct to the metal airframe, even more current will flow causing even more heat, and maybe something near by will catch fire.

The circuit protector should interrupt the current flowing in the wire before the insulation begins to melt. If the current isn't flowing there is no heat. If there is no heat, there is no fire (or melting insulation causing smoke, etc).

Sometimes things go wrong outside of this. UV rays can cause wire insulation to become brittle (older insulation), and then vibrations would cause the insulation to flake off. This may not be too much of a problem, but it may allow wires to touch, and then the current protection may not work properly. Imagine a 20 amp circuit next to a 5 amp circuit, and the 5 and 20 amp wires touch. The 5 amp fuse will do nothing because the 20amp circuit has taken up the load). Similar problems have happened, and fires break out even though the systems seem to be properly designed.

Should pilots be allowed to switch off circuits in flight? If smoke is in the cockpit, and it seems to be electrical, I believe they should be. Should pilots spend any time troubleshooting trying this circuit or that? I don't think so. If a pilot needs something to complete the flight, they should be allowed to try once, but once a  circuit is turned off, it should be left off. As much as possible, aircraft systems should be designed to enhance the pilots skills, not override it. When things go wrong, pilots need to land as soon as practicable, and have the systems checked out while safely on the ground.