 photo credit: Amazon |
| How can a UAV safely delivery packages? |
Are the FAA UAV (unmanned aerial vehicle) (or drone) rules taking too long and are they too restrictive?
It is not possible for an operator (remotely) to overcome all the risks of a UAV when overflying a community...
...since the failure we are concerned with most is loss of control.
Summary
- A UAV could be designed to meet existing certification rules
- UAV operations could be shown to offer equivalent safety as manned operations.
- UAV operations will need to be discrete and quiet, but yet still the public will be outraged by the visual distraction and that will lead to operational compromises
- UAV package delivery could save lives
- UAV package delivery could reduce carbon emissions
- UAV package delivery could reduce roadway congestion
A UAV hit me on the head!
There are two fundamental aspects to resolve: building the UAV and operating the UAV.
Public opinion will weigh into the decision making. Any approach needs to find the best means to gather public support.
One market proponent, Amazon, is particularly vocal for their objective of "Prime Air" small package delivery.
The benefits professed are about shortening the time to deliver a package, but also there is a cost benefit, since the propulsion is probably electric, plus the operation is expected to be automated.
UAV package delivery will probably take away package delivery labor, but it will create a demand for UAV products, maintenance, and operation. I hope this will be a beneficial transition, yet I fear for those employed driving a vehicle, certainly in the coming generation.
Removing package delivery trucks from roadways leaves more room for others, and reduces carbon emissions.
Can a UAV operate as safely as legacy aircraft while reducing the human toll for package delivery and while reducing carbon emissions?
Design for Safety
UAV package delivery presents new hazards that can't be ignored.
Whether a package is delivered, or delivered on-time, will have no safety effect (ignoring, say timely delivery of medicine or food).
There are high-level failures that do have safety effects.
- Failure of the UAV to follow the safe, prescribed flight path
- Failure of the UAV to avoid unexpected obstructions
- Un-commanded loss of payload
- Failure leading to loss (falling off) of UAV components
- Failure of the prescribed flight path to be safe
How do these failures have safety effects?
Aviation applies a methodical approach to understanding functional hazards and failure modes and effects through a mix of categorical and numerical safety processes.- If the UAV crashes into something, and that crash causes loss of control of whatever it hits, or the impact itself leads to injury or death.
- If the UAV crashes in such a way as to cause a distraction, such as falling amongst heavy highway traffic, leading to auto traffic to lose control leading to injury or death.
- If the UAV drops something that either impacts or distracts in a similar manner leading to injury or death.
If the FAA won't write new rules, why not apply the rules existing for manned aircraft?
- No single failure can lead to a UAV leaving a prescribed flight path.
- A UAV must have means to respond to unforeseen obstructions and failures leading to inability to continue along the prescribed flight path.
- It will be possible for UAV's to have contingencies to acceptable levels such that successful ditching will be the final means of escape from risk to humans and property.
- At any given time, a UAV should be able to ditch into safety crash zones even overcoming failures leading to loss of individual flight controls, and hopefully to adjust it's trajectory to dodge any last-second realizations.
The flight control system could be built through aggregation of independent motors, where each motor can cooperate with the other motors so that flight is coordinated, and that a motor not cooperating can be over-powered.
With enough independent motors, even two "run-away" motor failures could be overcome.
Route planning and contingency planning are paramount.
Real-time monitoring, both centrally and within each UAV, are paramount.
The design-assurance levels would be elevated, perhaps to the highest "catastrophic failure" level.
Constraining UAV components from unexpected departure will take structural design features to avoid the issue, and otherwise a fault-tolerant fail-safe approach.
The payload will need special handling considerations to ensure it is constrained, most likely dual-independent.
Most of each motor and the underlying assembly could be built with sufficient margins for constraint.
The propulsion source (propeller/turbine) could be constrained to some degree from ejection.
A UAV could be designed today to meet aviation safety analysis without breaking any traditional aircraft certification processes.
Sharing the Airspace
The introduction of UAV into controlled and uncontrolled airspace has a profound impact on the capacity for legacy air traffic to see and avoid UAV, and can further congest a system with more participation.
Limiting the UAV flight profiles to avoid legacy air traffic (exclusion zones) completely undermines the utility of the UAV service features directed to serve those inside the exclusion zones.
Can a UAV operate as safely as a human in a Visual Flight Rules (VFR) scenario?
Are we honestly assessing the ability for a VFR pilot to see and avoid, which is difficult at best?
The use of Traffic Information Services (TIS) adds a very real advantage in situational awareness.
A UAV can easily participate in TIS with transponder and with Traffic Collision and Avoidance System (TCAS) features.
A UAV could have sensors to in all quadrants for traffic conflicts, equivalent or better than a pilot using mostly a forward visual scan.
A UAV would favor corridors which could be crafted to avoid air traffic as much as possible, including close to airports.
Instrument Flight Rules (IFR) seems a much simpler challenge, where Air Traffic Control (ATC) is providing safe separation.
Large scale IFR UAV operations will quickly overwhelm ATC, even if including both voice and data link operational capacity.
My conclusion, the UAV will need to demonstrate equivalent capacity to legacy air traffic in both VFR and IFR.
VFR operations while remaining clear of clouds, even in uncontrolled airspace, is no panacea.
UAV operations within close proximity to persons, much like rotorcraft or lighter-than-air, will need some accounting, and here I think it comes down to the UAV being able to ditch safely as a key tenant.
Logistics and Cosmetics
Limiting the time the UAV is flying will reduce the hazards it presents.
One approach is to distribute the UAV bases so they are closer their destinations.
Distributing the UAV bases may be difficult if building large distribution centers.
Local UAV bases could be built in each area with a two-part flight plan:
- Distribution center to local UAV base along excluded corridor
- Local UAV base to destination using low-altitude hop in uncontrolled airspace
The distribution center to local UAV base leg could be handled by traditional trucking, as a first step.
Another approach could be a hybrid, where a mobile UAV base is filled with provisions for small locale, the mobile base is driven to the small locale from the distribution base, and then the UAV launches locally as a "last-mile" approach.
The last-mile approach would limit the altitude necessary, and hopefully shorten the path.
Another example of a mobile base could be circulating dirigibles where the UAVs hop aboard when over distribution centers and then drop off and return when over the destination.
A human operator can stand by with the mobile base, looking to assist if any UAV has difficulty.
A UAV overflight does not appeal to the general public.
Filling the skies with UAVs will not be popular.
The UAV needs to operate silently.
The UAV needs to be discrete.
A UAV operating at modest altitude is nearly invisible to a person looking for it, but these altitudes are most likely controlled and in use by legacy air traffic.
The public will advocate for limits to low-altitude UAV operations, and political tensions will result.
Peter Lemme
peter@satcom.guru
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