Club pilots regularly climb to 7500 metres in wave lift generated by the Australian Alps.

Mountain wave is usually accompanied by a region of strong turbulence (or rotor), that sits below the wave system, at times extending down to ground level.

The potential for rotor to cause damage has been known since the time of the Roman legions.

A wave flight inevitably involves a very rough aerotow up through the rotor. However, once established in the wave, pilots enjoy a magic carpet ride in smooth laminar flow air.

At the end of such a flight, equally rough conditions can be expected during the descent.

Our advice to any airline passenger who sees "turtle back's' in the sky out the window as they approach Canberra would be to tighten your seatbelt and decline a top-up of your coffee.

Rod Stone, president, Canberra Gliding Club

Blind to history

John Burns appears to be ignorant of the cultural, linguistic and religious diversity which existed among Australia's Indigenous peoples when Europeans first arrived (Letters, January 23).

He presents a supposedly "so much worse" fate imposed on "Aztecs, Incas, Africans, or those living in the Middle East", where new colonies [i.e. those political and military impositions which he charitably referred to as "countries"] "were created by just drawing lines on a map, ignoring local demographics and religious beliefs". But this is precisely what took place here also in Australia.

David Wilson, Braddon

New drug plan needed

In October 2016, what was then the largest drug haul for 2016 was achieved when approximately one tonne of crystal MDMA was saved from entering the community.

At the end of December 500 kilograms of cocaine was halted in NSW and 600 kilograms was intercepted in Tahiti.

Most recently a boat was intercepted off the coast of Tasmania carrying 186 kilograms of cocaine ("Arrests follow seizure of cocaine", January 19, p.14).

No matter the size of drug seizures, the amount of drugs onthe streets continually increases.

One would think if seizures were having a positive impact that they would decrease over time but data collected by the AFP shows this not to be so.

The AFP annual reports state that in 2009-10 drug seizures were 1244.9 kilograms, but in 2015-16 they were 9528.5 kilograms.

Whether so much money should be allotted to a system that is making little real impact surely deserves government attention. Alternative strategies such as decriminalisation and sharing the available resources more equitably with health deserve a trial.

M. McConnell, Giralang

Haters, take note

As Paul McGeough and others continue their vitriolic and visceral loathing of Donald Trump, they should take notice of Nicole Kidman and "support whoever is the President". Trump was democratically elected under the same system as their hero Obama and countless presidents before. They still fail to comprehend why Trump was the preference of the "deplorables" for President. Perhaps it's just wilful ignorance.

Owen Reid, Dunlop

The sight of Donald Trump taking his oath as President on two Bibles reminded me of the story of the wealthy American tycoon from Boston.

He said that he had made billions, but he had one ambition left.

He wanted to go to the top of Mount Sinai and recite the Ten Commandments.

A friend said: "Why don't you just stay home in Boston and have a go at keeping them?"

Fr Robert Willson, Deakin

Barbarians at gate

Would the Brits sell Whitehall for mandated demolition and redevelopment?

Did our government require the same for Sydney's Martin Place General Post Office?

Of course not. But the barbarians at the Department of Finance wants that for Anzac Park East and West.

The department snidely and cryptically sought public comment on the matter in the Christmas holiday period last year.

Stop them, Malcolm, now!

Jack Kershaw, Kambah

Exposed to asbestos

Unfortunately the ACT's liability for asbestos disease will not be resolved by the demolition program ("Inspections of Fluffy demolitions 'inconsistent"', January 21, p.3).

Since only 16 per cent of Mr Fluffy demolition sites received all four inspections mandated, our town council has failed in its duty of care and will remain exposed for mesothelioma claims for the next 50 or 60 years.

Gary J. Wilson, Macgregor

Get Jones off back

With his speedy and vitriolic attack on Gladys Berejiklian, in respect of her imminent elevation to Premier of New South Wales ("Jones claims Liberals shut down premier vote", January 21, p.6), Alan Jones has confirmed beyond doubt that he suffers from a form of "relevance deprivation syndrome".

Mr Jones was out of the country and could not have, and did not have, any influence at all over the triggering event – Mike Baird's resignation as Premier of NSW – and is irrelevant to consequent and subsequent events.

Let it go, Mr Jones.

Paul E. Bowler, Holder

Join the new revolution to keep public assets in community hands

E. J. Reeves (Letters, January 21) has reason to worry about the privatisation of ICONWater.

The ACT government is encouraged by the federal government to "recycle assets", which means sell public assets to private concerns.

Of the seven directors of ICONWater, only one has any qualification connected to water delivery. Most have a finance or economics background.

The government is under continual pressure from mainstream economic, media and political advisers to privatise public assets.

Some members of the ICONWater Community Consultative Forum have listened to the ideas on water tariffs suggested by the Independent Commission on Regulation and Competition and are concerned.

In response, we are forming an ACT Water Rewards Co-op of ICONWater customers to address the tariff issues and to provide an alternative for the government to the recycling of assets.

The co-op will ensure our water resources remain in community hands, bring fairer water tariffs while making our water assets available as collateral for investment loans from customers in the water using community.

We will be discussing the Co-op with both ICONWater and the government over the next few weeks. In the meantime, anyone who is interested can search for ACT Water Rewards on Facebook and follow the group.

Kevin Cox, Ngunnawal

Thanks for asking

My mother, who is 80 and in a government aged persons unit, was contacted today by a representative from ACT Housing.

She was asked if she was OK in the heat and if she needed anything.

Thankfully she doesn't, but what a wonderful service.

My mum was surprised and appreciative of this service.

Well done, Housing ACT.

Cassie Carey, Dickson

Address true need

Canberra's ratepayers provide a subsidy of more than $7 per trip to bus travel by Canberrans aged over 70 and by retirees aged over 60. These subsidies apply irrespective of assets or income.

The Superannuated Commonwealth Officers' Association (SCOA) wants the government to reduce the qualifying age for free bus travel from 70 to 65 ("ACT concessions for older Canberrans should be widened", canberratimes.com.au, January 20).

It argues public transport concessions encourage "older people on fixed incomes to be active". A $7 per trip subsidy to walking or cycling would do more to encourage older people to be active.

SCOA says it is "not asking for handouts but rather facilitating access to things and having only a nominal cost for older people and others in need".

But not all old people are in need. Many are wealthy. Many like me live comfortably on public service or other pensions.

SCOA argues some retired public servants struggle to afford basic amenities like travel. The costs of basic amenities should be allowed for in social security payments such as age pensions.

Reducing the Gold Card qualifying age would be an inefficient and unfair way to address inadequate incomes, or to encourage people to be active.

Leon Arundell, Downer

Wrong century

John Mckerral (Letters, January 23) asks why renewable energy needs subsidies if it is cheaper, as claimed, than new coal-fired power.

The answer is pretty obvious: present coal-fired power comes from old power plants, not new. This power is cheaper because it comes from plants that were mostly built decades ago, that have been written off financially years ago.

In fact, even when they were new they were often financially subsidised by taxpayers, through the state electricity commissions that built them.

Coal-fired power is also subsidised by the community every day, in ways other than this direct financial subsidy: through not recouping the costs of greenhouse emissions, health effects from local air pollution, and rehabilitation of the colossal scars on the landscape which it leaves.

Amazingly, the federal government seems intent on perpetuating all these subsidies, plus an infrastructure subsidy, for the massive Adani coal mine in Queensland.

If coal power were to meet its true costs, no subsidies would be needed for any competitor energy source. Coal-fired power would disappear, and this 19th century technology would be replaced by far better 21st century technology.

Paul Pollard, O'Connor

Speaks volumes

As a senior, I went to enjoy a film at the cinema on January 16. I was confronted by excess volume that exceeded my comfort zone. Upon complaining to the manager to lower the volume, I braced myself for the main feature, which was a blockbuster.

I lasted three minutes and stormed out to confront the manager and once again complained about the excessive noise.

Sadly, the message did not register with him and I obtained a refund.

May I make a suggestion that the whole system in presenting movies at cinemas, in general, be reviewed with the intention of considering clients' hearing tolerances.

Audiologists and audiometrists would be alarmed to know of this problem and would agree that excessive noise that the younger generation would be exposed to in this regard could possibly cause hearing impairment by the time they reach their 40s or 50s.

Peter Bazeos, Belconnen

Bush to blame

As we sweat in fear of North Korea's nuclear missile capability ("Fears that Pyongyang will launch", January 21, p.21), it's worth remembering who to thank – George W. Bush.

Clinton had a deal for North Korea to give up its nuclear activities in return for aid.

The North Koreans, the South Koreans and the Japanese were all on board.

Bush nixed the plan.

It seems quite likely that in 15 years we'll be reading similar stuff about Iran's nuclear activities, and we'll know who to thank for that.

S. W. Davey, Torrens

TRUMP PRIORITIES

Yes, President Trump, it would be nice if America and Russia could get along better. But it would be much more beneficial to the US and everyone else if America and China could get along better. That should be your priority.

Ron Walker, Campbell

Will no one rid us of this turbulent prez?

Peter Moran, Watson

THE WAY AHEAD

The British Century: 1815 to 1915 (Waterloo to Gallipoli).

The American Century: 1917 to 2017 (World War I to D. J. Trump).

The Chinese Century: 2017 to 2117?

Michael McCarthy, Deakin

LONG-SUFFERING

Pauline Hanson is reportedly annoyed at the Brisbane anti-Trump protesters' chant of, "Donald Trump go to hell. Take One Nation there as well." I agree with her. Those in hell are already suffering enough.

Eric Hunter, Cook

STREET SLAUGHTER

There comes a time where the law should lock in what the community expects. Stop sending users of dope to jail. Look what happened in Melbourne's CBD – domestic violence among other offences. Clear the jails of non-violent druggies, and let this low-life ice user suffer forever for allegedly killing and injuring so many, including beautiful little ones.

Greg Simmons, Lyons

All too often horrendous crimes are committed by persons described as "known to police" or on bail or parole. Couldn't the law devise a form of gentle surveillance of likely recidivists while still respecting the principle of innocent till proven guilty?

Barrie Smillie, Duffy

BURNS BRIGHTLY

Congratulations to John Burns of Hall (Letters, January 23). He courageously states the obvious, a position held in intimidated private by the majority of Australians from what I see and hear .

Paul O'Connor, Hawker

GROWING PAINS

For Northbourne we need trees that blossom in spring, shade in summer, colour in autumn and let the sun through in winter.

Kit Huang, Yarralumla

C'MON, SEVEN

On Sunday afternoon (January 22) Network Seven showed the Australian Open tennis on just one of its three channels. I couldn't watch either of the fourth round Murray-Zverev or Wawrinka-Seppi matches. Get your act together, Seven.

Don Sephton, Greenway

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