The Plan B
AMCA- The Horten wing-based Intruder Prof.
Prodyut Das
19 July 2025
This is a
discussion on using the Horten Wing technology to develop a 5th generation
“Malacca Straits” intruder using existing aggregates and resources.
The Horten History
The Horten wing is
best described by its German appellation Nurflugel i.e. “only wing”
aircraft. The Horten “Nurflugel” is an aircraft with only the wing and a
vestigial fuselage and is different from the Lippisch “Nurflugel” which has a
fuselage, a fin but no stabilizer. Two brothers, Reimar and Walther Horten,
over the period 1930-37 designed and built at home a series of 7 (Horten I to
VII) tailless gliders. The first one was so disappointing the brothers took it
home and burnt it. Because there was no fuselage and tailplane the weight and
drag were considerably reduced giving the powered versions of the Hortens
tremendous range. This inherent characteristic resulted in the twin Jet Horten
Ho 9 winning the Luftwaffe’s Drei Tausende (3- thousands) programme for
an aircraft with a 1000 km combat radius at 1000 kmph. with a 1000 kg.
war-load. An early engine related crash- at that time German engines were using
one tenth of the high temperature alloys required – prevented the full testing
to be done before the cessation of the hostilities- but the aircraft appears to
have been set fair to meet all design targets. Considering that the power came
from 2 x 9 kN ( sic) engines weighing
900 kgs each and with a s.f.c of 1.1
kg/kg of thrust the performance is impressive even today.
Understanding
the Nurfluggel.
There are various
mis-apprehensions about the tailless Nurfluggel -stability, safety and general acceptance
by the user. These are from a lack of information. Indeed, the very first tailless aircraft- the British
Dunne Tailless- was designed 1910 to increase flight safety by increasing
stability!
Tailless aircraft have a bad reputation because of problems which had nothing to do with the Tailless concept e,g. the DH 108s was because it was a wooden aircraft trying to break the sound barrier, the AW 52 possibly due to poor lay out, end plate fins on high AR wings. the Chance Vought F7U Cutlass which entered US Navy service in some numbers the reputation came from it having too low a power for a Shipboard fighter - when coming in to land on a heaving deck there simply not enough power left to correct any mistakes in the approach funnel.
The real problem
of the “Nur fluggel” was its lack of a fuselage; it was a “niche”
configuration, useless in general situations but if you were looking for low
RCS aircraft and long range with a limited/specialized war load then it is almost
unbeatable, which is why, even after 90 years, we see it’s influence in the
design of the American B2 and now, the Chinese Hong 35. Those people know what
they are doing.
With this as a
short introduction to the configuration, the question is raised that given the
present situation with the AMCA, about which I believe ADA is leading us up the
garden path, and given that though the B 52 is neither “stealth” nor “
super-cruising” and yet is a valued US war asset, then there is definitely room for a subsonic Indian 5th
generation a B 52 but with stealth- fulfilling
a role like a PI- 8 optimized for the anti- shipping role with the ability to reach the Straits of
Malacca. The aircraft will have the internal war-load of a B 52 but with a
smaller range- more in the region of a 2000km radius of action @ M=0.85. We
should not fall into the US trap of excessive specifications and then make the
second mistake of trying to achieve all that in one bold leap like the AMCA.
That is doomed to fail. However, the Plan B by being very circumspect about the
specifications, and using the factor of the high-quality missiles developed by
the DRDO to achieve mission objectives, done via a set of common-sense steps we
will be there very surely, on time and to costs.
AMCA Situation
summary
The Government of India is going ahead with what is a super cruising 5th generation AMCA. Having allotted Rupees 25,000 crores in 2025 values, it proposes to invest another Rs.66,000 crores for the 120 kN engine in collaboration with Safran where I believe we get to do the outer spool and the accessories.
After
70 years of Government led development if we still need “collaboration” under
“2nd fiddle” conditions isn’t it time to think that we pull the
Government completely out of weapons development? It is not doing the country
any good. Let the Government be an investor.
Given the present closer supervision- there was none in the earlier dispensation- the AMCA may roll out on time but there is good chance some unknown -unknown will hold up the project. What then? We don’t have a plan B and it will be the Tejas all over again. The Tejas has survived- in earlier eras it would be declared obsolete- because the growth of weapons capabilities compensated for its shortfalls in the platform.
It is also time to insist on at least two contenders. Imagine if
in 1989, when the ADA proposal failed to pass the IAF muster the HF 25 was
there running as a parallel project. ADA cannot at one time sup with the Devil of
the Import Lobby to ensure that there were no competitors to its design
efforts and blame the same import lobby for its
supposed ills.
The official answer given against having multiple projects at start is financial constraints prevents running parallel projects. This is willful ‘ostrich” disinformation . 90% of the project’s cost come after the fly off in testing -17, 000 hours of testing for the F 35 all variants, and certificating the aeroplane. That is why multiple proposals are run by the US. We spend 10%-20% more in the beginning but end up with alternatives and much useful data and avoiding imports and corruption.
How much should the additional competitor cost? The Government has
enough data. An actual corrected PDV figure i.e. Rs.@ 2025 would be around Rs.
1200 Crores per different type up to complete fly off tests. So at least two
proposals, for flyoffs has been the successful US pattern. Our Punditry scream
for US levels of funds but shrink in horror from competitive fly offs.
Change the
process of development to History based evolution.
The design of an
aircraft begins with an intense search of History. In the West they are so
steeped in History that they do not do it consciously. The Chief Designers have
lived through it. In our case we have to do it in a structured manner which if
you go about, it methodically might be an advantage by being bias free:
1.
Collect
all likely layouts including some of the concept studies which show
promise.
2.
Pass
collected layouts through the following filters
i)
When,
by who, what for?
ii)
Were
they prototyped? Flown? Results?
iii)
Selected
for production? If not why not? Rejection is often not for technical lacunae
and in any case our constraints may be different.
iv)
Cost
of project? Service records if any.
v)
Proportion
of “robust stealth” i.e. shape dependent, in the layout?
vi)
How
relevant to an Indian scenario
Going through
these filters about a dozen aircraft layouts seemed promising. Apart from the
usual suspects -F 117, F 35, F 22, F 32, XF 40, Horten /Gotha 229, there were
some unusual candidates- the MiG 21, The Folland Gnat and the Avro Vulcan, the
Swiss EW 20 series (for it’s nice bulged ‘universal” weapons bay-can that be
“stealth-ed”) and the SAAB Draken! Note that the last few in the clutch
includes conventional and Lippisch types.
Each candidate has
to be screened for its pros and cons but below is the case summary for the
Horten IX.
1.
It
was flown and would have met the performance demanded.
2.
Enough
information exists to create a NMG Horten 9 on the computer. It would be
possible to use the existing data to act as a firm base for proceeding with the
modifications necessary over 70 years with great confidence.
3.
The Horten 9’s dimensions of 16.7 mts wing
span , 7.8 mts length, 2.7 ht is a very
right size. It is small and simple enough to be built quickly and yet not too
small so that we get into Reynolds number problems when we scale it up to study
the Malacca Intruder. Empty weight 4590 kgs. Normal loaded 7484 kgs, MTOW
weight 8981 is just right for a TD to establish the technology and then be
scaled up to the desired.
4.
Just
by area reduction alone the aircraft will have a radar return varying from 0.2
(frontal) to 0,3 (side elevation) to 0.15 rear that of a Canberra at any given
range. This is any exclusion of further reductions due to shaping, surface
coatings, angle effects and surface finish.
5.
The
prototypes were built for 5 lakh Reichsmarks= $ 200,000 in USD 1944 by a
Locomotive and wagon factory, GothanaerWaggonFabrik, which indicates we will
not need exotic machinery demands e,g, 50K
ton press for PM turbine disc currently
doing the rounds. The nerve to ask!
6.
It
has an interesting structure- a steel tube space frame centre fuselage, wooden
wings with bonded wooden skins. It can be described as a transition between
steel tube and fabric structure to a stressed skin design. Sometimes less
advanced is better as in this case, very appropriate for a TD. The space frame
allows equipment to be fitted very quickly, the wooden skins can be replaced by
composites skins with modified contours as indicated during stealth
measurements in actual situ.
7.
The
engines are located such that a fairly large range of engines and inlets can be
tried easily to optimize the stealthiness.
8.
FBW
is not necessary at first flight.
The AMCA Plan
B TD.1100
The Ho 9 is so
perfectly sized for the task in hand that it is best to start with the Horten
design and only make what changes is deemed essential or obviously
advantageous. The replacement of Jumo engines and fuel system by the TFE 334
high bypass turbofans of 18.6kN as used in bijjets will see a weight reduction
1100 kilos. The Ho 9 was built using “scrounged” parts- the undercarriage came
from a bomber so some weight savings would be possible using better modern
equipment. The differences are put in the table. The disposable weight is
considerable and much equipment can be added or removed,
The Horten
and the TD
Sl.No |
Item |
Horten 9 |
TD |
Remarks |
1 |
Span |
16.76 |
16.76 |
|
2 |
Length |
7,5 |
9.5 |
|
3 |
Height |
2,7 |
2.7 |
|
4 |
Wing Area |
52.49 |
|
|
5 |
Empty wt. |
4590 |
4200 |
|
6 |
Weapons Load |
2x500 kgs,
4x30 mm |
See. notes |
A 4 mts x1.6 mts Universal Bay for ASMs eg, Harpoon, etc. Pockets for AAMs, 1 x 23 mm. |
7 |
Normal Loaded |
7484 |
7484 |
|
8 |
Max Loaded |
8981 |
11,000 kgs |
|
9 |
Power |
2x Jumo 9.81 kN |
2x TFE 731-5 @ 20.6 kN |
|
10 |
Fuel Load |
2620 |
|
|
11 |
Max W/L |
171 |
209 |
|
12 |
T/W at Max wt |
457kg/kN |
266kg/kN |
|
13 |
Max. span loading |
|
|
|
14 |
Max. Speed |
962 kmph |
1070 kmph approx..M 0.92 |
|
15 |
Max Range |
1896 km. |
|
|
T is common sense
that if an aircraft could be developed 80 years ago in war time Germany for a
then value of $ 200,000 and built by a Locomotive and Wagon company and even
today the basic idea is held to be valid then we can generally agree that a
Horten type flying wing can be built with basic facilities and low cost within
a short time.
I was alarmed to
find that the specific fuel availability (kg. of fuel available per kN of cold
thrust ) of the proposed AMCA is actually 20% less than that of the Tejas. Again
common sense says if there is less fuel to burn per unit installed thrust then
the range will be less i.e. the AMCA will have shorter range and endurance than
the Tejas. Here we are trying to enter into expensive collaborations to ensure
getting a super cruising, an ability that is already compromised by a basic
proposal which itself is short legged so what is this about super cruising? If
point is valid then super cruising for how long and to what utility? If this is
the quality of proposal scrutiny it is heading for the docks. Who passed it?
Why did ADA overlook such a simple obvious
point?
In the 5th,
generation super cruise is the deliberate technology trojan Horse designed to
keep the competitors out. We seem to have fallen for it once again or is their
a deliberate plan. If so by whom?
The Government
must investigate why certain projects get so needlessly mired with problems
that should have been nipped in the bud.
Given the above
situation a TD based on the Horten Nurfluggel would be a firm step in securing
5th. Generation technology. It would give us the data to confidently
design, using supply chain security firmly in the foreground, two 5th
Generation type.
1.
A
stealth intruder of the class of a Canberra i.e. 5000 kg weapons load but with
perhaps 60% more range. Tis would use a rectified Kaveri or any suitable secure
turbofan engine of the 50kN class.
2.
A
Heavy Intruder of similar configuration with a 10 ton war load and a combat
radius of 2000 kms.
3. The Project costs asked by the State enterprises and Laboratories are ridiculous. It is time the Government got out this business. It will find that project costs will come down by a factor of five to ten times.
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