My condolences to the family and friends of the pilot and the passengers of this terrible tragedy.
Without pre-judging the outcome of the accident investigation, the following thoughts may have some relevance...
The de Havilland Beaver floatplane has a long history of fatal accidents caused by low altitude stalls (see TSB Canada Aviation Investigation Report A15Q0120 below).
Unfortunately in the floatplane configuration, the Beaver aircraft is necessarily operated at low altitude from rivers and lake valleys that are typically surrounded by high ground with gusty changing wind velocities.
Added to that challenging environment, is the Beaver's modest performance envelope, low power/weight ratio, high drag form, the aircraft's stall behaviour and its stall warning characteristics.
After a deadly Beaver stall/crash accident in which killed a pilot along with his 5 passengers in Ontario 23 Aug 2015, the Transportation Safety Board of Canada's investigation report
recommended that commercially operated de Havilland Beaver aircraft should be fitted with a stall warning systems.
The installation of stall warning systems were recommended because of inadequate natural stall warning provided by the aircraft itself and rapid onset of an accelerated stall.
The extracts below are from the TSB Canada Aviation Investigation Report A15Q0120:
Aviation Investigation Report A15Q0120 - Transportation Safety Board of Canada
In the controlled conditions of certification, the stalling of the DHC-2 was described as gentle. However, as is the case for many other aircraft, a stall in a steep turn under power triggers an Incipient spin with few or no signs of an impending stall, and the flight path changes from horizontal to vertical. In low-altitude flight, stalling followed by incipient spin, no matter how brief, prevents the pilot from regaining control of the aircraft before impact with the ground.
In 2014, Transport Canada and the manufacturer, Viking Air Limited, recommended that stall warning systems be installed, but only 4 have been installed on Canadian‑registered DHC-2s. There are currently 382 DHC-2s registered in Canada, 223 of which are used in commercial operations.
Level of risk is determined by the probability and severity of adverse consequences. Given the number of DHC-2s without a stall warning system in commercial operations, combined with the fact that low-altitude manoeuvres are an integral part of bush flying, it is reasonable to conclude that a stall at low altitude is likely to occur again. Because stalls at low altitude lead to catastrophic consequences, this type of accident carries a high level of risk.
Until, at a minimum, commercially operated DHC-2s registered in Canada are required to be equipped with a stall warning system, pilots and passengers who travel on these aircraft will remain exposed to an elevated risk of injury or death as a result of a stall at low altitude.
Therefore, the Board recommends that
the Department of Transport require all commercially operated DHC‑2 aircraft in Canada to be equipped with a stall warning system.
TSB Recommendation A17-01
Appendix C – TSB aviation investigation reports on accidents involving aircraft that stalled and were not equipped with stall warning system
Accident Type Fatalities Summary
A14O0105 DHC-2 Beaver 0 The float-equipped DHC-2 Beaver aircraft (registration C‑FHVT, serial number 284) rolled to the left prior to the flare. The pilot attempted to regain control of the aircraft by applying full right rudder and right aileron. The attempt was unsuccessful, and the aircraft struck rising tree‑covered terrain above the shoreline. The aircraft came to a stop on its right side and on a slope. Two of the 3 people on board received minor injuries. The aircraft had no stall warning system.
A12O0071 DHC-2 Beaver 2 The DHC-2 floatplane (registration C-FGBR, serial number 168) stalled and crashed during a go-around while attempting to land. Two of the 3 people on board drowned. The aircraft had no stall warning system.
A11C0100 DHC-2 Beaver 5 The DHC-2 floatplane (registration C-GUJX, serial number 1132) stalled and crashed during takeoff. All 5 people on board received fatal injuries. The aircraft had no stall warning system.
A10Q0117 DHC-2 Beaver 2 The DHC-2 amphibious floatplane (registration C–FGYK, serial number 123) stalled and crashed during takeoff. Two of the 5 people on board received fatal injuries. The aircraft had no stall warning system.
A09P0397 DHC-2 Beaver 6 The DHC-2 floatplane (registration C-GTMC, serial number 1171) stalled and crashed during takeoff. Six of the 8 people on board received fatal injuries. The aircraft was equipped with a stall warning system, but it was not functioning, and the TSB identified this as a cause or contributing factor.
A08A0095 DHC-2 Beaver 0 The DHC-2 floatplane (registration C-FPQC, serial number 873) stalled and crashed while the crew was attempting a forced landing. Five of the 7 people on board sustained serious injuries. The aircraft had no stall warning system.
A05Q0157 DHC-2 Beaver 1 The DHC-2 floatplane (registration C-FODG, serial number 205) stalled and crashed during takeoff. The pilot, who was the sole person on board, received fatal injuries. The aircraft had no stall warning system.
A04C0098 DHC-2 Beaver 4 The DHC-2 floatplane (registration C-GQHT, serial number 682) stalled and crashed on approach. The 4 people on board received fatal injuries. The aircraft had no stall warning system.
A01Q0166 DHC-2 Beaver 3 The DHC-2 floatplane (registration C-GPUO, serial number 810) stalled and crashed on approach. Three of the 7 people on board received fatal injuries. The aircraft had no stall warning system, and the TSB found this to be a risk factor.
A01P0194 DHC-2 Beaver 5 The DHC-2 floatplane (registration C-GVHT, serial number 257) stalled and crashed on approach. All 5 people on board received fatal injuries. The aircraft had no stall warning system; the TSB noted this fact under "Other findings."
A00Q0006 DHC-2 Beaver 3 The DHC-2 (registration C-FIVA, serial number 515) stalled and crashed while climbing. Three of the 6 people on board received fatal injuries. The aircraft had no stall warning system.
A98P0194 DHC-2 Beaver
(modified: maximum weight increased) 0 The DHC-2 floatplane (registration C-GCZA, serial number 1667) stalled and crashed following a missed approach. None of the people on board were injured, but the aircraft sustained substantial damage. The aircraft had no stall warning system, and the fact that the pilot had no warning of the impending stall was identified by the TSB as a cause or contributing factor in this occurrence.