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How good is a TB-20 on grass? Short field?

Let me re-phrase it:

The whole point of a grass strip which is less than really good condition is that nobody wants to spend money on it.

This is really tangential to the topic but if you have a bunch of say 10-20 people operating SEPs and between them they cannot get 100k (the cost of one Annual, perhaps) together to ensure a good operating base, they are in the wrong business.

But if a strip is in a poor condition then we are not talking about anywhere near 100k. You could level it and mole drain it into a ditch, with a scavenge pump, for something like 20k.

I fully understand the poor buggers who want to tarmac it but cannot get permission, or judge that doing it would be too provocative (747s flying in, is the usual local protest briefing).

Other “grass” threads here here here

BTW, referring to the original post, the term “short field” is specific in FAA-land to both grass and tarmac. So to answer that Q: the TB20 is fine on tarmac down to about 450m (e.g. Wangen Lachen LSPV) providing you land at more or less the right speed. Less than that, get a Maule or a C182

Administrator
Shoreham EGKA, United Kingdom

My wife has suggested we can get a bigger plane. I will do ANYTHING to keep her happy. I do like the option of grass and short though, so a TB20 is probably not the ride. They look great though!

Tököl LHTL

If “something bigger” is the objective, I guess a followup question could be how do the larger retracts, eg. PA32 handle grass?

tmo
EPKP - Kraków, Poland

@ WiskeyPapa,

What tyre pressure do you use for grass?

For all practical purposes, tyre inflation pressure = ground pressure, and whenever this exceeds the ground bearing capacity, we’re in the landscaping business.

With typical light aircraft tyres, inflating to more than about 18 psi needlessly degrades performance on soft ground. Depending on the wheel and tyre, it may be safe to go lower, and there are plenty of backcountry pilots running 8.50×6 Goodyears etc. at 12-15 psi on Cleveland rims. By all means check for tyre creep post- and pre-flight, but I’ve never had tyres (even 31" diameter) creep on 6" Cleveland rims down to 8 psi.

The tyre pressure recommended in your flight manual may be appreciably higher. Higher tyre pressure is needed on tarmac to increase hydroplaning speed, to reduce wear, or for heavy landings with sideways drift – not that we would ever do that

Last Edited by Jacko at 28 Apr 22:30
Glenswinton, SW Scotland, United Kingdom

@Jacko
I have always used POH pressure. I don’t go into rough fields, generally well maintained grass, but I’ve just replaced the tires so maybe should consider this.

Tököl LHTL

Peter wrote:

This is really tangential to the topic but if you have a bunch of say 10-20 people operating SEPs and between them they cannot get 100k (the cost of one Annual, perhaps) together to ensure a good operating base, they are in the wrong business.

Sure, if you’re thinking about owners of high end tourers. But the point of having clubs is to make flying affordable even to people with average incomes.

ESKC (Uppsala/Sundbro), Sweden

WhiskeyPapa wrote:

I do like the option of grass and short though, so a TB20 is probably not the ride.

What does short mean? Grass, you can get airfields which have grass runways which look and feel like golf greens (without the holes of course) and others which defy description. As you won’t probably base your plane at one of the latter fields, it is mainly runway lenght which is your concern. And there, obviously, most fast travellers will not have the STOL capabilities of your current plane, there is next to none which does unless you want to go for a AN2 which is arguably bigger but may be a tad over the top of what you are thinking of.

Clearly, the grass conditions described in the posts here are something which is a major factor with ANY airplane, also your Morane won’t like a muddy field full of potholes. The question is, are you going to base your new ride there or do you simply have the capability to go there when necessary and want an idea about what kind of rwy you can do.

The TB20 is maybe not the ideal plane for this, even though it is a distant relative of your Morane and per se was definitly not constructed with just asphalt runways in mind. The landing gear would actually suggest that. The POH is definitly the place to see that, Peter has posted the graph already. The POH also gives the following factors:

10% increase in distances for short grass, 25% increase with long grass. (Page 5.7)

MTOW take off performance at 2000 ft ISA is indicated at 1560 ft roll and 2469 ft total distance on asphalt, or 1845 ft roll and 2976 ft total distance at ISA +20°
On grass, these values would increase to 1716 ft / 2715 ft on short grass and 1950 ft / 3086 ft with long grass for ISA
With ISA +20° you’d get 2030 ft / 3273ft on short grass respectively 2306 ft / 3720 ft with long grass.

Metric this means at MTOW you see a ground roll of 523m / total distance of 827m on short grass at ISA and 562m / 907m with long grass
With ISA +20°, a TB20 at MTOW needs 620m to get airborne with short grass and 1 km to get over 50ft. With long grass, it will take 700 m to get airborne and 1134m to get to 50 ft.

That does give you some ideas about what you need to expect at 2000 ft elevation at MTOW.

There is also a table for 1075 kg RTOW, which of course is a lot less. The take off performance there is massively better, of course.
At ISA and 2000 ft Roll is 905 ft, Total 1399 ft on asphalt. Short grass, that is 1000 ft / 1538 ft. (Metric: 305/487m). Long grass: 1131 ft / 1748 ft. (Metric 344/530m)
At ISA+20 and 2000 ft Roll is 1070 ft and total distance 1655 ft on asphalt, short grass that is 1177ft /1820 ft (Metric: 358m/554m). Long grass: 1337ft/2070ft (Metric 408m/631 m)

So at reduced take off weight with roughly 270 kg load (including fuel) you can get quite decent values, but of course this is very restrictive in terms of what you can load.

So the values indicated by the previous posters are pretty much ballpark. The TB20 definitly is not a STOL plane per se, it is more of a plane which requires pretty long runways to comfortably operate from.

Then again, POH values are optimum values flown by test pilots and black magic and all that as many will say but they are all we have. Of course, there is no direct definition on what short and long grass is. And clearly, it will not take any account for runways which are a pit of mud.

I would say, with decent runways, the TB20 can certainly do the trick but it needs proper calculation and due diligence like any airplane. At least in the POH they do give some good information.

People do operate the TB20 off grass, as this video shows.



I don’t know this airfield but the take off roll looks rather short.

What your Morane can do in terms of STOL, not many larger ones can match and of those who can, not many are travellers. I have heard good things about the performance of the C182 in terms of short runways but I don’t have any figures handy. Of the newer travellers like Cirrus, TB20 and so on, none of them are really for that small runways. Vintage Mooneys E and C have very good runway performance, but they might not take grass runways too kindly with their gear and can develop fuel leaks if operated on bad runways regularly, yet they do quite well in the rough.




and



as an example.

these videos also show that while a lot can be done with a type, there is a lot of personal preferrence of what to do and what not. There are people who won’t go on grass no matter what, others who will if they know the field or have done it many times before, depending on airplane and experiences. Even jets land on grass occasionally:



Best regards
Urs

Last Edited by Mooney_Driver at 29 Apr 12:27
LSZH(work) LSZF (GA base), Switzerland

If you need an airplane that can do pretty much anything, buy a C182. The Swiss Army Knife of SEPs.

The discussion of there being possibly too much elitism is here. I think it is definitely a good topic.

Administrator
Shoreham EGKA, United Kingdom

@ Mooney_Driver
Thanks for the thoughtful post and videos!
I’m not now based off grass (LOAN) but used to be (LHBS).
My desire is to be able to land at grass fields in reasonable condition down to about 400-500 meters. That opens up a whole range of options in traveling, and in some cases means you don’t need to rent a car, but can land right where you want to and walk or take a taxi.

As an example, in Sicily flying from Ragusa-Guibiliana (the hotel, 750 meters asphalt, manageable for a TB-20) to 550 meter soil Agrigento (AG05) to check out the ruins and then to Marina DI Modica (RG02) 650 meters grass to go swimming. The options in a STOL plane are real and they mesh well with flying in Europe.

https://www.thethinkingtraveller.com/thinksicily/guide-to-sicily/archaeological-sites-in-sicily/the-valley-of-the-temples-agrigento.aspx

https://en.m.wikipedia.org/wiki/Agrigento_Airfield (not now abandoned as stated here)

I agree with 172driver that a 182 is an option. They certainly are capable, especially when light.

Last Edited by WhiskeyPapa at 30 Apr 07:35
Tököl LHTL
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