He provided a false statement to his medical examiner and the Civil Aviation Authority (CAA) when he completed his medical forms in November 2016 and April 2017, the summary of facts said.
He failed to disclose he had been seeing a doctor for stress and anxiety-related issues, and that he was prescribed various medications "that are not considered compatible with aviation safety".
They included sleeping tablets and anti-depressant medications.
The CAA only found out about the medications after receiving an anonymous tip off, and launched an investigation.
"The defendant said he failed to disclose that information because he feared that his medical certificate, and thus his ability to fly, would be compromised if he had," the summary said.
He also failed to tell the CAA of his change in medical status.
During the medical application process, the medical examiner considers the applicant's age, personal health history, and family health history before recommending what should be included in routine examinations and whether further medical tests should be conducted.
Lucas was required to complete an assessment every six months.
"A pilot's health status may have a significant influence on performance, behaviour and flight safety," the summary said.
"This is why it is important that a pilot's medical fitness has been certified prior to exercising the privileges of an aviation licence."
There is a higher medical standard that must be met to receive a class one medical certificate - what Lucas was operating on - which allows pilots to fly commercially.
"This higher medical standard reflects the commercial nature of this type of flying activity, and offers assurance to paying members of the public that the pilot flying their aircraft is fit enough to perform the required flight duties and is unlikely to become incapacitated during the flight."
Lucas has been remanded to August for sentencing, while his careless flying charge will be dealt with later this year.
He made headlines last year after clambering relatively unscathed from a helicopter that had crashed into the Pauatahanui Inlet.
That crash came about due to a tailboom pylon rupture, causing the craft to spin out of control.
Immediately after the crash, Lucas told media he knew something was wrong when he felt "quite an intense vibration that got worse and worse" before the helicopter began to rotate.
"I just carried out what are considered to be the normal emergency procedures and got away with it."
He tried to stop the machine from rotating, but hit the water with a "significant impact".
